人造石材平整度公差的允许值应不大于规定厚度的（）%。
A.5
B.6
C.7
D.8
参考答案：A
—We don't permit________in our school.Would you please put your cigarette out?
—Forgive me. I didn't know.[ ]
A. to smoking
B. to smoke
C. smoking
D. having smoked
到两定点F1(-2，0)和F2(2，0)的距离之和为4的点M的轨迹是______。
A．椭圆 B．线段 C．圆 D．以上都不对
