What is the weather like here this summer? It seldom rains. B has been there, and C has been there.

It is a sentence pattern,

Therefore, exclude a.

D

over there

be

The subject of the sentence pattern is in the back, which is little in this sentence.

rain

Describe rain in singular form.

It's a complex number. number

B uses the perfect tense, because what the weather is like in summer happens before asking questions, so it uses the perfect tense.