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. | 
