63. 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) whether tourists will continue to visit game parks and see rhinoceroses after their horns are

(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

Why the verb following "after" should be the present perfect? Even after reading the explanation in OG11, I still think present tense is ok too.

根据whether>if，排除DE

A proposal has been made to trim the horns from rhinoceroses to discourage poachers

就是说决定已经作出，

after their horns are trimmed似乎时态还是过去完成时更好，与前面对应

且参观的是已经被修剪去角的犀牛