Hey voodoo_child,

Really interesting question - you may find some more technical explanations out there, but practically speaking here's how I chose B over D:

-"...and that they later evolved" in D seems a little illogical. Evolution is a long process, so it seems odd to me to delineate between mammals moving to the water AND THEN (but never beforehand) evolving in to modern whales. More logically, the move to the water was part of that evolution. So the "and that they later" to me suggests an illogical meaning.

-B is considerably more concise than D, and I don't see any problems with B. Typically I'd say if you're down between two and one is more concise, go with the shorter one.

-This may be too technical so it's a lesser reason to make this distinction, but in D "fossils provide evidence in support of..." may also have a less-than-perfectly-logical meaning. "in support" really has to correspond to the verb "provide", and since fossils can't really have any intent (they're inanimate objects) the meaning of "in support" seems off.

For this one, here is where I'd recommend another practical (and not as purely technical) strategy. Ask yourself for another situation in which you'd say X did Y in support of Z. Maybe "I raised my hand in support of the proposal". What was "in support"? It wasn't your hand - it was the raising of your hand. Which should indicate to you that the real antecedent of the "in support" modifier isn't the object, it's the verb. And since, in this sentence, the verb "provide" belongs to something that can neither support nor criticize, D doesn't have a perfectly logical meaning...

IMO B

Interesting question. Took almost 1:45 min. After looking at the question I noticed two things : a) "theory that" should be correct b) there is no comma between evidence and supporting. This means supporting is modifying evidence (sounds logical too).

A. supporting the theory of land mammals returning to the water that later

B. supporting the theory that land mammals, after returning to the water,

C. that supports the theory of land mammals that returned to the water and that later (two parts before and after AND are not parallel in structure.)

D. in support of the theory that land mammals returned to the water and that they later (even though both parts of "AND" seem parallel, second "THAT" actually refers to the mammals, but in this sentence it means "theory evolved into modern whales" , which is nonsensical)

E. of support for the theory of land mammals that returned to the water and after