烧结空心砖的主要原料有()
A.黏土
B.电石膏
C.煤矸石
D.砂
E.页岩
参考答案:A, C, E
Do ________ you think is right _________ difficulties you may have.
A.what; however
B.that; whatever
C.whatever; however
D.what; whatever
※ [18~20] .( 3 )
A. .
B. .
C. .
D. .