According to two teams of paleontologists

[MichaelS7]

Hello teachers!

i have a question in C&D. can i eliminate those answers because 'they' here at the end has an unclear reference?

what's more, when should we add 'subject+verb'after THAN? I mean, here we say 'dolphins are more closely related to ... than to...' but not 'dolphins are more closely related to ... than THEY ARE to...'. Is there any situation where we should add it?

thanks in advance!

[RonPurewal]

Hello teachers!

i have a question in C&D. can i eliminate those answers because 'they' here at the end has an unclear reference?

^^ no. in context, it's perfectly clear that "they" = "whales, porpoises, and dolphins"... so it's fine.

remember—
DO NOT think about "pronoun ambiguity"!
"pronoun ambiguity" is not tested on this exam!
the INTENDED meaning of a pronoun should ALWAYS be clear from context. if the intended noun is present in the sentence—and matches the pronoun (in terms of singular/plural)—then the pronoun is fine.

[RonPurewal]

what's more, when should we add 'subject+verb'after THAN? I mean, here we say 'dolphins are more closely related to ... than to...' but not 'dolphins are more closely related to ... than THEY ARE to...'. Is there any situation where we should add it?

thanks in advance!

^^ both versions are fine.

in general, the correct answers are written as efficiently as possible—so, IF YOU HAVE A CHOICE between these two, you should pick the one that doesn't use unnecessary words.