Sentence Correction

21. A proposal has been made to trim the horns from rhinoceroses to discourage poachers; the question is whether tourists will continue to visit game parks and see rhinoceroses after their horns are trimmed.

(A) ...
(B) whether tourists will continue to visit game parks to see one once their horns are
(C) whether tourists will continue to visit game parks to see rhinoceroses once the animals' horns have been
(D) if tourists will continue to visit game parks and see rhinoceroses once the animals' horns are
(E) if tourists will continue to visit game parks to see one after the animals' horns have been

OA is [spoiler](C)[/spoiler]

What is wrong with (A). I can't understand how "their" is ambiguous as it is close to rhinocerous.

Is that the problem or is the "have been" part more correct than "are" ?

Previous explainations have not helped much. Can someone clear my doubt please?

It is a pronoun reference problem. In A, "their" refers either Visitors or rhinoceroses. So discarded.

In D, no ambiguous pronoun refernce is there. So it is the answer