以下的题目按我问的答,1.The islands developed on their own for 80 milli

以下的题目按我问的答,1.The islands developed on their own for 80 million years and _______ have many rare animals found nowhere else.A.soon B.so C.early D.yet 我选D结果错了,请问选哪个?为什么+翻译.2.—How do the shops make money if they sell at such low prices?—Manufacturers,it seems,are willing to bring down prices _______ big volume purchases.A.under the name of B.on behalf of C.in return for D.in preparation for 选哪个?为什么 +翻译 3.According to the school rules,no student _______ go out of school without the permission A.will B.must C.may D.shall 哪个?为什么 4.Some modern teaching equipment as well as hundreds of computers _______ to ten Hope Schools in South China.A.were sent B.was sent C.have sent D.had been sent 这题答案是B,为什么D不可以选?5.Unless you call me to say you’re not attending my birthday party,I’ll see you at it.翻译.