_________(61)A.prevent B.preserve C.presume D.pre

1，－5，13，－29，______ A.－61 B.－39 C.39 D.61

The purpose of the wearing rings used in a centrifugal pump is to _____.A.prevent an inter

The main function of piston compression rings is to _______.A.prevent excessive cylinder l

Setting a sealing equipment astern on the tailshaft can’t ____.A.prevent the seawater from

According to the news item, partially hydrogenated oils are used to______.A．prevent heart

61._________A. processesB. producesC. possessesD.