by three and a half billion years agoBy three and a half billion years ago the highly complicated molecule DNA had emerged.这句话中的by和ago为什么可以同时用?不都是在.之前的意思吗?

THREE AND A HALF怎么样 three-and-a-half billion three years and half a year three and-a-half times中文是什么? about three and a half months ago three months and half 和three and a half months 有什么区别? by three and a half billion years agoBy three and a half billion years ago the highly complicated molecule DNA had emerged.这句话中的by和ago为什么可以同时用?不都是在.之前的意思吗? It took us ----to finish this work.A .three hour and a half B.three and a half hour C. three and half hours D.three and a half hours 详细讲解一下 three and a half hours的近义词,急用! —How wide is the table?—It is ___ .A.three foot and one half foot B.three and half feet C.three—How wide is the table?—It is ___ .A.three foot and one half foot B.three and half feet C.three and one half feel D.three and one half foot答案 Which has a high infection rate and could reduce wheat output by half.output by half 1：Miss Gao will stay in Nanning for about ______( )A:three months and a half B:three month and a half C:three and a half month D:three months and half2：He's been a soldier for nearly ______( )A:half and two years B:two and half yearC:two years an She has been skating for _____.A.three and a half years B.three and half a year为什么选A?是因为第二个后面没加s吗。a half year=half a year began to skate__ A for three and a half years B three and a half years ago.说明理由 for也不可以是用在一般过去时的吗? We have discussed this topic three and a half hours为什么不加for为什么不是We have discussed this topic for three and a half hours three and half years 等于哪一个词组? Three and a half days () not a short time A is B are children's day is on june___ eath yearThirty pulus ninrty-three is____Please wait here,and I'll be back in____ hours.A two and half a B two and a half C half and two D two a half