OG16 75题 after，sequence与过去完成时

Macklemost

75. 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

解释上说：过去完成时是为了强调事件发生的先后顺序， 可是曼哈顿（guide 8 P.110）说， 如果句子里有表示时间顺序的词"after","before"， 就不需要再强调时间顺序了。到底听谁的

AMBER513

如果一个句子里面已经明确出现过表示时序的词语例如before, after, in the 1990s, etc. 那么再来用帕萨特perfect就是redundant的。因为past perfect也是一种用来明确时序的方法，已经有了别的东西存在，就没有必要再用了