压力容器的封头形式一般选用()形封头。
参考答案:凸
Personally I think it is the sales manager, rather than the sales girls, _____ to blame.[ ]
A. is
B. that is
C. are
D. who are
免疫系统包括()
A.胸腺
B.骨髓
C.淋巴结
D.脾
E.周围淋巴结