液氮贮存罐的内外罐间呈真空状态,目的是()
A.便于罐体升压
B.保证罐体的安全
C.减轻罐体的重量
D.增强罐体的绝热性能
参考答案:D
____ the students likes the paintings. Which is wrong?
A.The teacher as well as
B.Nobody but
C.The teacher besides
D.All except
有关畸胎瘤的描述,不正确的是
A.好发于卵巢、睾丸
B.由2个胚层以上的组织构成
C.多呈囊性,囊内充满油脂、毛发
D.未成熟型可见原始神经组织
E.肿瘤起源于生发上皮