prep1-45

红尘道士

(E) Applying a new method for analyzing the chemistry of tooth enamel, scientists have examined molars of prehuman ancestors and determined
答案E中，现在完成时怎么和过去式并列？
我感觉答案应该是
(E) Applying a new method for analyzing the chemistry of tooth enamel, scientists  examined molars of prehuman ancestors and determined

-- by 会员 红尘道士 (2010/3/21 15:21:59)

(E) Applying a new method for analyzing the chemistry of tooth enamel, scientists have examined molars of prehuman ancestors and （have）determined
E中不会是省略了后面一个have把，有这种用法么？