一般情况下,并山水下体积和水上体积分别约为冰山总体积的_________和_________。
A. 1/8,7/8
B. 7/8,1/8
C. 2/8,6/8
D. 6/8,2/
A large valve,usually installed above the ram preventers,that forms a seal in the annular
A. annular blowout preventer
B. annulus
C. accumulator
D. automatic choke