By the end of last month中的by是什么意思?不太懂哦

by the end of last By the end of last month中的by是什么意思?不太懂哦 by the end of last month ,they___(build)five bridge By the end of last year he______about 1500 English words. by the end of last month 上个月末? by the end of last week用什么语态 -----of last term,students had made lots of new friendsa.by the end b. in the end c.at the end d. to the end he finished writing the novel____of last month.A.at the end.B.by the end of 选哪个?为什么? By the end of last week, Mr Fang ____ (sell)thousands of cards . by the end of last month ,they had finished half of their work 是什么时态 John said to his parents,''I had learned 500 chinese words by the end of last term.''变为间接引语by the end of last term不用改成by the end of the term before吗? Tom had finished his homework at the end of last month.可以是at the end of 它和by the end you 有什么不同? By the end of last year,they _____(learn) two thousand English words. They----[learn] over 2000 English word by the end of last term. They___(learn)several French songs by the end of last term.填什么?为什么? By the end of last month,they _____________(结婚)for 50 years. By the end of last term they ________ over 1000wordsA have learnedB had learned By the end of last term,they ___(work)there for ten years.能讲出为什么吗