A:it
B:one
C:those
D:them
A:____
B:Good morning.
B:My name is Jack.
B:I'm twelve.
B:Table tennis.
B:OK.
A.How old are you?
B.Good morning.
C.Let's play it in the afternoon.
D.What's your name?
E.What's your favourite sport?
“善不是一种学问,而是一种行为”这告诉我们( )
如图是英国科学家普利斯特利的一组实验,请你利用所学的生物学知识来解释相关的实验现象.