Bunuel
If the new department store
would open by Thanksgiving, it will be attracting many holiday shoppers.
(A) would open by Thanksgiving, it will be attracting
(B) would be opened by Thanksgiving, it would be able to attract
(C) was opening by Thanksgiving, it would be able to attract
(D) was to open by Thanksgiving, it also will attract
(E) opens before Thanksgiving, it will attract
OFFICIAL EXPLANATION
One problem with this sentence is that the first clause of an “if x, then y” sentence should not contain the conditional verb “would”. The other problem is that the tense of the second clause is incorrect. This is an “if x, then y” sentence in which the first clause concerns a possible future event, and the second clause concerns a predicted consequence of that event. The first clause should therefore be in the present tense, and the second clause should be in the simple future tense (“it will attract”).
(A) This choice is incorrect as it repeats the original sentence.
(B) The first clause of this version is incorrect because: (1) it still contains "would", and (2) there is no good reason to use the passive voice ("be opened") here. The second clause is incorrect because it changes the meaning of the sentence by saying that the store would merely "be able to" attract holiday shoppers.
(C) "If it was opening" is always incorrect. For a possible future event in an "if" clause, you should normally use the present tense and the indicative mood: "If it opens". [If you wanted to indicate skepticism about the possibility that the store will open, you could use the subjunctive mood. But the correct way to do that would be to say "If it opened" or "If it were to open" or "If it were opening".]
The second clause of this sentence is also incorrect, as explained in (B).
(D) "If it was to open" is always incorrect. As noted for (C), you should normally say "If it opens". [If you wanted to change the meaning of the sentence, which is not a good - 50 - idea in sentence correction problems, you could use the subjunctive mood. But the correct way to do that would be to say "If it opened" or "If it were to open" or "If it were opening".]
In the second clause, "also" is unnecessary and somewhat illogical. The action in the second clause will happen, if it happens at all, as a later result of what happens in the first clause. The word "also" contains a suggestion of simultaneity that is inappropriate in this context.
(E) CORRECT. We now have a correct “if x, then y” sentence, in which the first clause is in the present tense and the second clause is in the simple future tense.