在B细胞上不出现下列哪个标志（）
A.EB病毒受体
B.Ⅰ类MHC抗原
C.Ⅱ类MHC抗原
D.C3b受体
E.CD2抗原
参考答案：E
额定载重量为2000kg的电梯轿厢面积不应大于()
A.4.2
B.2.4
C.5.0
D.2.0
A tug is approaching a broken down steamer in moderately heavy weather preparing to take it in tow. In most cases the（）.
A.steamer will drift stern downwind
B.tug will drift faster than the steamer
C.tug should approach stern to
D.tug should approach from downwind
