Question

19．This medicine    millions of people's lives since it was put into use．（　　）

• A． is saving
• B． will save
• C． has saved
• D． had saved

Answer 1

分析 這種藥自投入使用來(lái)就挽救了數(shù)百萬(wàn)人的性命．

解答 答案為C
根據(jù)從屬連詞since可知，需要用現(xiàn)在完成時(shí)，表示從過(guò)去某個(gè)時(shí)間點(diǎn)開(kāi)始到現(xiàn)在的動(dòng)作，而且這個(gè)動(dòng)作對(duì)現(xiàn)在有影響．
此處since引導(dǎo)時(shí)間狀語(yǔ)從句，since后接表示一個(gè)時(shí)間點(diǎn)的句子，說(shuō)明從過(guò)去的時(shí)間點(diǎn)到現(xiàn)在的這段時(shí)間里的動(dòng)作．現(xiàn)在完成時(shí)的構(gòu)成為has/have+過(guò)去分詞．故選C．

點(diǎn)評(píng) 注意since引導(dǎo)時(shí)間狀語(yǔ)從句時(shí)，主句的時(shí)態(tài)一般為現(xiàn)在完成時(shí)．