选哪个,请给出原因.-----Where's your assignment?-----________.A.I had already handed it in.B.It was handed in.C.It'd been handed in.D.It's been handed in.

选哪个,请给出原因.A.involving,that B.involved,that C.invovled,where D.involving,whichThere is a new problem_______in the popularity of private cars ______road conditions need to be improved. 选哪个,请给出原因.A.where B.that C.when D.whichChina's new food law provides for a food recall system______producers have to stop production if their food isn't up to standards. 选哪个,请给出原因.-----Where's your assignment?-----________.A.I had already handed it in.B.It was handed in.C.It'd been handed in.D.It's been handed in. 选哪个,请给出原因.A.were brought up B.brought up C.have been brought up D.are bring upWhether we find a joke funny or not largely depends on where we_______. 选哪个,请说明原因, I didn't see Laura at the party last night.Do you know（ ）?A.what happenedB.where she has been选哪个呢?请给出理由,谢谢 they were pushed farther and farther until they were confined to a reservation in--is now SouthDskoda.a.whichb.whatc.where选哪个为什么请给出详细解释 植物细胞中线粒体和叶绿体中哪个CO2浓度高?请给出详细原因… 选哪个,请给出原因.A.used B.has been used C.using D.is usingThe computer,now______by millions of people,has changed the world 选哪个,请给出原因.A.in B.for C.on D.withThe temperature today is very low.It is quite cold______June in shanghai. 选哪个,请给出原因.A.proving B.proved C.was proved D.has been provedThe cause he had devoted himself to _______a perfect success. 选哪个,请给出原因.A.while B.whether C.what D.whichWe thought there were 5 students in the dining hall,_______,in fact,there were 40. 选哪个,请给出原因.A.near B.upon C.within D.aroundIt saves time in the kitchen to have things you use a lot _______easy reach. 选哪个,请给出原因.A.searching B.to search C.searched D.searchAfter hours________,their patience was rewarded and they found what they were looking for. 选哪个?请给出原因.A.leaving untreated B.leaving untreating C.left untreated D.left untreatingIf_______,the wound in your arm may become infected. 请给出正确答案,并解释原因. 一个环与甲基相连,当发生取代反应时,取代哪个位置的氢?--有机化学.为什么?请给出原因! When I called you this morning,nobody answered the phone.Where _______?A.did you go B.were you 选哪个?为什么?请说出两者的具体区别,这是一个高考题，谁能给出个合理的解释？