An integral part of a blowout preventer that serves as the closing element on an open hole，and whose ends do not fit around the drill pipe but seal against each other and shut off the space below completely is the（）.

A.shear ram

B.blind ram

C.pipe ram

D.annular ram

患者，女性，32岁，“胃切除术”3年。近1年患者头晕、心悸、气短，疲乏无力。诊断为缺铁性贫血。

导致患者贫血的原因可能是

A．饮食中供铁不足
B．铁吸收不良
C．育龄期女性需铁量增加
D．损失铁过多
E．铁不能利用