We use__or___before when we mention them for the first time.We use __when we mention them again

问题描述:

We use__or___before when we mention them for the first time.We use __when we mention them again
A.the;a;an B./;a;the C.a;/;an D.a;an;the

D(前面的意思是泛指,后面是指特指)