现今使用数量最多的玉材的是（）。
A.和田玉
B.独山玉
C.岫山玉
D.昆仑玉
参考答案：C
___ an answer from her husband, Emily decided to send him another email.
A．Not having received
B．Having not
C．Receiving not
D．Not receiving
简述氨合成用催化剂的活性测试原理和方法？
