A:I hope so
B:Yes, I have
C:I hope not
D:Yes, I’m afraid so
假设过氧化氢生成氧气的快慢与催化剂种类有关.
听第三段对话,回答两个问题。
下列装置不能达到实验目的是( )
_______ he is ill, he is not here today.