prototypevenom wrote:
I have two doubts which are as follows..
1) 'that' cannot take place of which to define nonrestrictive clause but 'which' is can be used for defining clauses?
Can you explain further what you mean by 'defining clauses'?
You're correct that there's a difference between 'that' and 'which' in terms of meaning. One way to see this difference is by looking at sentences like these ones:
A. Go to the third house that is red.
B. Go to the third house, which is red.
In A, 'that is red' is an 'essential' modifier. It tells you that we're
only considering red houses, and we don't care about any houses that aren't red. In other words, the house being red is 'essential' to the meaning of the sentence. In this case, you'd look only at the red houses, and find the third one of those houses (even if it wasn't the third house on the street.)
In B, 'which is red' is an 'inessential' modifier. You're still looking at all of the houses, red or otherwise. But you also have a little extra info, that might or might not be useful: the third house happens to be red. In this case, you'd go to the third house on the street. You'd expect it to be red, but you're really just looking at whether it's the third house.
That said, this is a
meaning difference, not a grammar one. On the GMAT, here's the only situation where you'd really worry about this. First, you'd have to have a split between 'that' and 'which' in the problem, where some answer choices used 'that', and some used 'which'. Second, one of the meanings would have to be illogical or nonsensical, or at the very least, substantially change the original meaning of the sentence. In that case, you'd pick the option that had a logical meaning.
Quote:
2) it follows a comma and precedes by a comma?
or just preceds a comma and not ends in a comma?
example- I like oranges, which are not sweet, better than mango.
or I like oranges, which are not sweet better.
You want a comma both before and after. However, the GMAT won't test you on that specifically. (In other words, you'll never have to decide between two sentences, where the only difference is where the commas are placed.) Commas can be a useful clue to tell you where a modifier begins and ends, but you don't need to worry too much about the exact rules for them.