raghavs wrote:
3. There is speculation
that increasing cold weather was what may have been responsible for the Anasazi move from Mesa Verde to sites in other canyons.
(A) that increasing cold weather was what may have been
(B) whether increasing cold weather was what was
(C) that increasingly cold weather was what had been
(D) whether increasingly cold weather may have been what was
(E) that increasingly cold weather may have been
let me try to say something.
in a and b, "increasing" modify "wheather" grammatically. this modification is not logic. it should modify "cold" and become "increasingly". this error is easy.
"speculation" must go with "that-clause", and can not go with "whether-clause. we can remember this idiom through the meaning of "whether-clause". d is gone.
in c, "had been" is not justified. we need a sequence to use had done. grammatically, "what had been" must happen before "was what". but this is not logic. c can be correct if a shorter version is " cold weather was responsible...".
in "that-clause" after "speculation" both confirmation verb "was" or " possibility" verb can be used, I think. This point can not be explained in grammar books but must be infered by us.