If birds did not have wings, they would not have been able to fly

It was a tough call between C and D but D seems to be the right choice.

Unless = if not
Use of unless in the first conditional requires use of will / won't in the 2nd conditional.

did not have (negative) = simple past form + would not be (negative) = conditional ------- correct.

Reto it would be nice if you could provide the OE also along with the OA

Thanks

My choice Option B.

This question seems to be testing (past + conditional) structure.

Reto., please post the OE. Very nice question.

Im happy you like it. Discussion tonight including OA

As usual an amazing question reto.

Would love to see the OE..

Hypothetical Subjunctive requires "If X, Then Y" construction.

Then is missing from A, B and D. Hence eliminate them.

We are left with C and E.

E has a tense error. "would not have been".

C is better.

The contention that C and D are grammatically ok, but D is to be dropped for being stylistically wordy floats on vapor-thin reasoning. We can understand two choices being grammatically correct but differing substantially in meaning, but not on wording. Do we get such almost identical twins on the Test? But this topic is okay since it brings out the nuances of trciky conditionals, especially the second and the third, into open.

Dear Experts,

Is the usage of "had"(past perfect) in option C correct?

IMO- We need to use past perfect only to express sequencing of two events.. we don't have another past event in option 'c'.

Then how it is correct... Please advise where am I going wrong in above reasoning.

Hi,
this is present unreal situation or a hypothetical situation..
In these scenarios HAD can be used..

another example
if I had a million rupees, I would buy an island.
If he had known of the outcome, he would not have gone to that extent.

I'm confused why we can't go for Past Perfect Tense Usage for Conditional Statements (If X, Then Y).
I thought both options B & E adhere to this.
If I had no doubt, I would not have posted this comment

sayantanc2k wrote:

scorp16 wrote:

I'm confused why we can't go for Past Perfect Tense Usage for Conditional Statements (If X, Then Y).
I thought both options B & E adhere to this.
[color=#00aeef]If I had no doubt, I would not have posted this comment

The rules for if-then construction are as follows:

CASE I - Unlikely event in the future: IF hypothetical subjunctive, THEN conditional (would).

If I went to school ( tomorrow), I would be sick... The sentence implies that I am unlikely to go to school tomorrow. But if I went (tomorrow), I would be sick.
If I had doubt, I would post this comment.....The sentence implies that I am unlikely to have a doubt (in future). But if I had (in future), I would be sick. Here "had" is NOT SIMPLE PAST, but hypothetical subjunctive that is unlikely to happen in future.
If I had no doubt, I would not post this comment.... the sentence implies that you are unlikely not to have a doubt ( you are likely to have a doubt in future).

CASE II - Past event that never happened in the past: IF past perfect, THEN conditional perfect (would have)
(CASE I CANNOT be used, if a past event is described that never happened.)

If I had gone to school yesterday, I would have been sick.
If I had had doubt, I would have posted this comment. ( had had is past perfect of had)
If I had had no doubt, I would not have posted this comment.

Therefore, your sentence ( "If I had no doubt, I would not have posted this comment") mixes up a hypothetical subjunctive in the IF clause with a conditional perfect in the THEN clause, and is therefore incorrect . You must use a past perfect, neither simple past, nor hypothetical subjunctive with a conditional perfect, when you are describing a past event that did not happen.

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Hello Sayantanc2k,

Can you please breakdown the answer options as well?

I am still not sure about how to apply this rule to the answer options.

Please help

We need to correct the OA on this one. D is the only possible answer. (I should add that we will never correctly eliminate a correctly-written answer simply because it is slightly longer than another choice.)

Others have discussed the flaws in the use of hypotheticals in some of the wrong answers, but a simple way to eliminate A, B, and E is that they talk about birds' flight as if it is restricted to the past. Rather, since we're talking about an imaginary situation in which birds don't have wings, it's correct to talk about their flight as a future hypothetical ("they would not be able to fly").

The problem with C is that it uses the word "unless" to refer to a condition that we know is true. This works grammatically, and if we were to diagram the logic it would come out to the same meaning, but the sentence is still flawed because it implies that we aren't sure whether birds have wings. In fact, it seems as if we suspect that they don't! This is absurd, so we have to reject C.

Imagine another scenario. "Unless you want to win a million dollars, you won't enter the contest" is logically equivalent to "If you enter the contest, you want to win a million dollars." However, the first seems much more humorous. Are we warning potential contestants that they might win a million dollars? Or how about this? "Unless humans are mammals, they are not warm-blooded." Are we unsure about these facts? Of course not, so we should say "If humans were not mammals, they would not be warm-blooded." Now we are talking about an imaginary situation rather than questioning the current facts.

Going through the discussions, I have a feeling there is some misconception about the word ‘had’
‘Have’ is the bare form of the verb in the meaning of possess.
Had is the past tense of the verb meaning possessed.
Had had is the past perfect of the verb meaning I had possessed prior to I possessed.
Pl note that the word ‘had’ when used alone without another past tense verb such as ‘had’ or for that matter, any other past verb, is only denoting a past tense. Therefore, there is no question of ascribing ‘had’ as a past perfect verb in choice B, C and E. Choice A and D are straightforward past tenses.
If you want to convert B, C and E to past perfect tense clauses, then you have to say ‘had had’ in all the cases. Ex: B. If birds had had no wings, C. Unless birds had had wings, and E. Unless birds had had wings
It will be easier to understand the use of 'had' in various contexts with the following example.
Two years ago when I entered day trading, I had had 10 million rupees in the bank -past perfect
Last year, I had only one million in the bank – past tense
HTH

Can somebody tell what the correct answer is and the proper explanation for that. It seems that many people, including few moderators, have a difference of opinion about the correct answer[OA]. Can someone please tell the correct answer along with explanation.

If birds did not have wings, they would not have been able to fly

My 2 cents of reasoning, and somehow I am more inclined towards D in terms of meaning of the sentence; and not the 'wordiness' - GMAT rules always put meaning first and wordiness and 'sound' of sentence later in the importance ladder
A. If birds did not have wings, they would not have been - clear case of tense mismatch - no need for past perfect
B. If birds had no wings, they would not have beentoo colloquial in construction
C. Unless birds had wings, they would not be as per explanation; unless = if then; which in terms of meaning is not true.
Unless is more definite - 'unless there is evaporation there will be no clouds' - here I doubt the usage of unless - if I think of it critically; some birds have wings and still cannot fly. So how come such assurance?
D. If birds did not have wings, they would not be I had picked this as simple past tense and usage of 'if-then'
E. Unless birds had wings, they would not have been issue in tense

Madhavi1990, the simplest way to translate "unless" is "if not." So C translates logically to "If birds did NOT have wings, they would NOT be able to fly." For those who are comfortable with conditional logic and contrapositives (not really a GMAT skill), this also means "If birds WERE able to fly, they WOULD have wings." (-W --> -F, F --> W). This doesn't tell us anything one way or another about whether all birds with wings can fly. It only tells us that wings are necessary for flight.

So logically, this all makes sense and is consistent with reality. The problem is just in the hypothetical form of the sentence, which seems to indicate that birds probably do not have wings, as if wings are just a possibility we are imagining. A better use of this form would be for something more speculative or even unlikely: "Unless you wished to give offense, you should not have told that joke." "Unless she exited the highway, she is probably stuck in that traffic jam." These are uncertain things we are considering. We wouldn't say "Unless I was born, I wouldn't have gone to school." At best, it looks like we are trying to prove that we must have been born. In the original sentence, we are not trying to prove that birds have wings, but rather to point out how necessary they are for flight.

One problem here is that this sentence is a bit more silly and content-free than anything we'd see on the GMAT. It is merely stating the obvious, so it's hard to divine the author's intention. This makes it harder to select a good answer.

Like DmitryFarber, I also think C change the intended meaning of the original sentence.

Let's see the following sentences;

If X happens, Y will happen => Y may happen without X => X is not necessary to happen Y.
Y will not happen unless X not happen => Y will not happen without X => X is required to happen Y.

Now let, X= Birds did not have wings and Y= Birds would not be able to fly.

So, the original sentence becomes if birds did not have wings, they would not be able to fly. That means birds would not be able to fly for other reasons apart from that they have no wings. Lacking wings is not necessary for not be able to fly. On the other hand, choice C changes meaning by saying that birds would not be able to fly ONLY because they had no wings. But this is not the original meaning. Birds may not be able to fly for other reasons such as injury or anything like this.

Answer would be D.