Hi j_shreyans,
The usage of the word "that" is often circumstantial. There are certain situations in which you MUST use it:
eg. "Command" Verbs....
The bank manager demanded THAT the teller open the vault.
In other situations, the word "that" can be tied to another grammar rule (as a pronoun or as part of a parallel phrase).
Still, in other situations, the issue is the use of "that" vs. "which." The word "that" denotes specific/restrictive ideas, while the word "which" refers to vague/non-specific ideas.
This is all meant to say that in most cases you need to have the full SC prompt with answer choices to determine whether to use the word "that" or not.
GMAT assassins aren't born, they're made,
Rich
