问题补充:
单选题Spaceexplorationbeganinthe1960s,andsincethenaboutfivehundredpeopleintospace.A.have traveledB.traveledC.had traveledD.are traveling
答案:
A解析考查时态。根据since then可知与完成时连用。故A正确。
时间:2019-10-24 01:51:29
单选题Spaceexplorationbeganinthe1960s,andsincethenaboutfivehundredpeopleintospace.A.have traveledB.traveledC.had traveledD.are traveling
A解析考查时态。根据since then可知与完成时连用。故A正确。