A.較大 B.較小 C.保持不變 D.其它三項(xiàng)都不對(duì)
A.<20cp B.<30cp C.<40cp D.<50cp
A.降低循環(huán)泵壓 B.提高儀器信號(hào)質(zhì)量 C.減小對(duì)井下儀器的沖蝕 D.降低對(duì)儀器信號(hào)的干擾