prosaicblabber wrote:Hi Guys ,
I'm always confused when it comes to modifier questions involving "which" "that".
Consider the following examples :
1) Rings made from pearls which are .......
2) Rings made from pearls,which are ...
3) Rings made from pearls that ...
4) Rings made from pearls ,that ...
A) Do you find all the constructs grammatically corect ? ( forget about the dotted lines

)
B) How does usage of that and which brings about a change in meaning/intention ?
C) How does use of a comma affects the object/subject being modified ?
Take above examples to answer these question ( no matter how stupid they may appear to you

)
I am no Expert.. But Let me share my thoughts here.
Out of the 4 constructions,
1) Rings made from pearls which are .......
4) Rings made from pearls ,that ...
It is very unlikely that you will see these two on GMAT. If you find something like this, they are almost always wrong.
Coming to 2) Rings made from pearls,which are ...
Which normally introduces a non essential modifier. Here which refers to the preceding noun - Pearls.
John reached the house, which is on hill-top
The sentence makes sense even with out the nonessential modifier. John reached the house.
Which is on hill-top is just additional information provided about the house.
On the other hand,
3) Rings made from pearls that ...
"that" introduces an essential modifier. "that" also modifies the preceding noun.
John reached the house that is on hill-top.
This is stressing on the point that John reached the house that is present on the Hill-top, not the road-side one.
that is on hill top is providing the essential information of John's action.
Hope this helps!!