The first sentence
- Think of it this way:
- My sister tells me she is in one of the "study rooms" at the library. She says:
- 1) "I'm in the third study room, which has a door knob."
- 2) “I'm in the third study room that has a door knob."
says she is in the third study room, which just so happens to have a doorknob. Of the many study rooms, she is in the 3rd study room.
The second sentence
says she is in the third door-knobbed room, which may or may not be the third study room. Maybe the 2nd, 4th, and 7th rooms have door knobs. In this case, she is telling me she is in the 7th room, not the 3rd room. You see, you need to use the word "that" when the information conveyed after it is essential to the meaning of the sentence because it restricts the scope of what you are talking about.
Notice how the words after “that” in the second sentence actually change the meaning of that sentence.
No longer are you talking about any study room---you’re talking about only the study rooms that have door knobs. If you ever see a sentence on the GMAT that uses “that”—see if you can take out the phrase afterwards without altering the meaning of the sentence. If the phrase RESTRICTS the set of items you are talking about, then that’s correct.
If, however, the phrase only adds detail without restricting---then that’s a RED FLAG
. You should use “which” instead and add a “comma”.
What you’ll see on the test:
“The development of new classrooms that aims to accommodate the growing student body has been halted.
Don’t use “THAT”...because if you use “that” it implies some classrooms accommodate the growing student body while others do not...You should change it to this:
The development of new classrooms, which aims to accommodate the growing student body, has been halted.