环空返速为()时,有利于钻井液形成平板型层流。
A.0.5一0.6m/s
B.0.6一0.8m/s
C.0.8一1.0m/s
D.1.0一1.2m/s
参考答案:A
We __________ so tired. We've only been to a party.
A.mustn't have felt
B.wouldn't have felt
C.shouldn't have felt
D.couldn't have felt
有关脑胶质细胞瘤的表述,错误的是()
A.是脑瘤中最常见的类型
B.属于神经上皮性肿瘤
C.好发于儿童
D.常致颅内压增高
E.肿瘤的恶性程度与瘤组织中内皮细胞增生的程度正相关