下列混合材料中，具有火山灰性的有（）。
A.煤矸石
B.硅灰
C.烧页岩
D.火山灰
参考答案：A, B, C, D
There _____ a basketball match between Class One and Class Three this afternoon. [ ]
A. is going to be
B. will have
C. are going to be
D. is going to have
确定广告主题时应注意哪些问题？并举例说明。
