Explanation:

Answer: (a)

Were the clothes dried in the lawn by mother?

(a) Did the mother dry the clothes in the lawn?(Correct)

(b) Did the mother dried the clothes in the lawn? (Third form of the verb used with did)

(c) Did his mother dry the clothes in the lawn? (Incorrect word)

(d) Had the mother dried the clothes in the lawn? (Tense has changed)

First