58._________A. improvements B. factorsC. jobsD. m

The process of scavenging a two－stroke／cycle diesel engine serves to____________.A.improve

离心泵转速为2900r／min，叶轮外径为200mm，可估算其扬程约为________m。A.42B.58C.116D.168

【C2】______A．openB．coveredC．secretD．improved

______ do you think _____ we should do to improve our English？A、／; whatB、what; thatC、wha

63._________A. increaseB. reduceC. improveD. remo

_________(62)A.ignore B.improve C.like D.determine