炸高影响射孔的穿深和孔径，最佳炸高通常为射孔弹聚能罩开口直径的（）倍。
A、2
B、3
C、4
D、5
参考答案：B
Here ______some pieces of news, and I want to know what the latest news _______. [ ]
A. are; are
B. is; is
C. is; are
D. are; is
黏多糖病酶活性测定的样本为( )
A．肝细胞B．骨骼C．尿液D．脑脊液E．血细胞、血清或成纤维细胞
