电灯的拉线开关应接在（）上。
A、火线
B、零线
C、地线
参考答案：A
If you had joined the chat room ten minutes ago, you _____ what we were talking about.
A．will know
B．are knowing
C．can know
D．would have known
95％的睾丸肿瘤是生殖细胞肿瘤，其基本组织类型包括（）
A.精原细胞瘤
B.胚胎癌
C.畸胎瘤
D.绒毛膜上皮癌
E.精细胞瘤
