A.must be B.may have been C.can have been D.could be ,为什么呢,Although there is no life on Mars now,some scientists think that there______some form of life a long time ago.
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![A.must be B.may have been C.can have been D.could be ,为什么呢,Although there is no life on Mars now,some scientists think that there______some form of life a long time ago.](/uploads/image/z/7357953-57-3.jpg?t=A.must+be+B.may+have+been+C.can+have+been+D.could+be+%2C%E4%B8%BA%E4%BB%80%E4%B9%88%E5%91%A2%2CAlthough+there+is+no+life+on+Mars+now%2Csome+scientists+think+that+there______some+form+of+life+a+long+time+ago.)
A.must be B.may have been C.can have been D.could be ,为什么呢,Although there is no life on Mars now,some scientists think that there______some form of life a long time ago.
A.must be B.may have been C.can have been D.could be ,为什么呢,
Although there is no life on Mars now,some scientists think that there______some form of life a long time ago.
A.must be B.may have been C.can have been D.could be ,为什么呢,Although there is no life on Mars now,some scientists think that there______some form of life a long time ago.
表示曾经有过,所以是Have been
表示猜测,所以是may
Although there is no life on Mars now, some scientists think that there_may have been some form of life a long time ago过去完成时延续性动作,强调对现在有影响
may 在此处表示一种猜想而不是“将要”,整个意思是:也许有过生命,故选b