Are they making the mark? [ ]
A. No, they can't.
B. Yes, they are.
答案：B
" stop _ _" the teacher said angrily.[ ]
A. To talk
B. talk
C. talking
透视检查的基础是利用X线的是（）
A.光学作用
B.生物作用
C.穿透作用
D.电离作用
E.荧光作用
