【C20】______A．worryB．fearC．carelessnessD．hard work

塔筒筒壁的混凝土验算等级不应低于______。A．C30B．C25C．C20D．C15

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

It is the director, and not the members of the board, ______ the most.A．who worryB．whom wo

【C20】______A．withB．offC．beforeD．from

______, the instruments would be damaged.A．If having handled carelesslyB．To handle careles

57._________A. hopeB. fearC. waitD. look