Hei Wrote:How come it doesn't require a "that" between "said" and "a squirrel"?
you're going to hate this answer, but ... because it just doesn't. :)
that's actually a serious answer: in the majority of uses like this (she believed (that)..., it has been said (that)... etc.), it's acceptable to omit the word 'that' if the construction's meaning is still clear and unambiguous.
in this case, an extra factor in favor of omitting 'that' is the occurrence of the word 'that' just a few words away; a sentence containing the words '...so prevalent
that it was said
that...' would be awfully ugly.
Hei Wrote:Under what circumstances can "that" be omitted when a clause is introduced?
Thanks in advance.
see above. the cases in which it can be eliminated are many and varied.
a thought that should provide some consolation: i'm pretty certain that the gmat won't include a problem that hangs on the presence vs. absence of the word 'that' alone. note that, in this problem, the presence/absence of 'that' isn't really an issue, because all the choices except a and d can be eliminated on other grounds of grammar/usage. both of those remaining choices - a and d - omit the word 'that', so you don't have to make that decision yourself. (notice that the choice between a and d comes down to the rhetorical meaning of those two choices.)