_______ she was invited to the ball made her very happy.
A.What
B.That
C.When
D.Because
B
The best time _________to Beijing is in August.[ ]
A. come
B. to come
C. came
D. of come
化学无处不在,请用所学的化学知识解释,为什么煤炉火越扇越旺,而蜡烛一扇就灭.