属于间接火源的是（）
A、明火
B、电火化
C、雷击
D、自燃
参考答案：D
Liu Dehua, Zhou Jielun and Lin Junjie are famous _____ their pop songs.[ ]
A. as
B. for
C. with
D. of
链轮由哪几种材料制成，它有何特点？
