Question

They hadn't expected so much rain,

a) had they?
b)did they ?​

Answer 1

a) had they?

Step-by-step explanation:

in what I have read if there is a negative question tag yo have to change it to positive question tag.

in here the negative question tag is hadn't so you have to change it to had they.

Answer 2

Answer: b) did they ?

Explanation: It makes more sense to me than choice a) had they ?