腰椎正位中心线经以下哪个部位垂直射入暗盒中心（）.
A、脐孔
B、脐孔上3cm
C、脐孔下3cm
D、髂棘
E、以上都不是
参考答案：B
-What about _________ to practice pronunciation?
-Well, that's good. It helps me a lot. [ ]
A. read loudly
B. reading aloud
C. read loud
D. reading loud
内环境是指（）
A.细胞外液
B.细胞内液
C.透细胞液
D.体液
E.血浆
