同类型土分层填筑时,一种土最小填筑厚度为( )。
A.30cm
B.40cm
C.50cm
D.60cm
参考答案:C
______ girls took part in the Super Voice competition, but only a few of them succeeded. [ ]
A. One million of
B. Thousands and millions
C. Millions of
D. Two millions
火灾的三要素是指可燃物、助燃物和点火源。