[讨论]LZM 3-13，没有人问过

LZM 3-13

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

A  whether the tourist will continue to visit game parks and see rhinoceroses after their horns are

B whether the tourist will continue to visti game parks to see one once their horns are

C whether the tourist will continue to visit game parks and see rhinoceroses once the animal's horns have been

D if the tourist will continue to visit game parks and see rhinoceroses once the animals horns are

E if the tourist will continue to visit game parks and see one after animals horns have been

答案为C， 我不明白为什么once 后用的是完成时阿？ 可以用过去时态的虚拟语气么? 多谢指点！！

have been 表示砍断角是发生在客人去参观之前

个人意见。。。

谢谢楼上！