since then后面加什么时态?Eg.Scientists __________ (build) a station at the South Pole several yearsago.Since then they________________ (get) muchinformation about the South Pole.怎么填?

since then后面加什么时态?Eg.Scientists __________ (build) a station at the South Pole several yearsago.Since then they________________ (get) muchinformation about the South Pole.怎么填? since前面加什么时态,后面又加什么时态? since then后接什么时态 Since后加什么时态 since一般后面跟什么时态 since前加什么时态啊? since then和什么时态连用, 一定是现在完成时么 since then用于什么时态过去时可以吗 since then用什么时态只能用现在完成时吗 very 后面加什么时态? if后面加什么时态 then后加动词的什么时态 加since的句子时态的用法句子后面+since,前面的时态应该用什么.比如 I___here since I was a child.A.have been staying B.had been staying C.stayed D.have stayed E.had stayed 求英语复合句时态公式!比如When后面用什么时态?Since后面用什么时态?While后用什么时态?If后用什么时态? should后面加动词的什么时态 if后面加动词的什么时态? thought 后面加什么动词时态 finished后面加动词的什么时态