заместо точек: The grass is wet. It ... A)has been raining

The grass is wet. It has rained.

The first sentence is in Present Indefinite (is). We use Present Perfect in the second sentence. Present Perfect I used for past action which result connects with present.

Present Perfect is formed with the help of the auxiliary verb to have. We use has for the third person singular (he, she, it). We use the third form of verbs (rained).

Negative have / has + not + the third form of verb.

 It has not rained.

Interrogative have / has + subject + the third form of verb.

 Has it rained?