【C17】______A．constructedB．sentC．anticipatedD．based

（1）a＋18=______＋______　　　a×15=______×______（2）m×2.5×0.4=______×（______×______）（3）（a＋b）×C=______×_____

【C17】______A．practiceB．pleasureC．problemD．habit

It’s high time we ______ him a regestered letter.A. sendB. sentC. has sentD. had sent

It is essential that these papers ___________ in time.A. are sentB. be sentC. will be s

强心苷苷元结构和强心作用有一定的关系，强心苷苷元母核C17位连接的_________及_________构型是不

— ___________________— Once or twice a week.A How