Presumably you're looking for an explanation, and not simply the answer here!
Sometimes when choosing between modifiers, we have to look to meaning, not simply to grammar. Consider the following:
The list of groceries that is hanging on the refrigerator is long.
The list of groceries that I need to buy is long.
In each case, the core of the sentence is the same: The list... is long. In the first sentence, "list of groceries" was a single noun idea - the list of groceries was hanging on the refrigerator. In the second, it doesn't make sense to buy a list of groceries, so "that I need to buy" must be modifying only groceries.
In your sentence, a list can't exhibit a preference, only animals can. That subordinate clause starting with THAT is modifying ANIMALS only. However, LIST (OF ANIMALS) is still the subject of the verb HAS BEEN EXPANDED.
When looking at C, D, and E, the issue is IDIOMS. The correct idiomatic form is PREFERENCE FOR, so the correct answer is D.
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
