现在完成时和过去时态的区别
The monent the 28th OLympic Games________open,the whole world cheered.
A.declared B.have been declared C.have declared D.were declared
为什么选D不选B?
Since the deadly H5N1 bird flu virus_____not only in Asia but also in Europe and Africa,migratory birds have been regarded as the carriers.
A.discovered B.was discovered C.had discovered D.have been discovered
这题又为什么选B不选D啊?不是有个SINCE啊?