Question

Which of the following sentences properly uses a hyphen?

Answer 1

A- My maternal grandmother is sixty-six.

B is incorrect as thunderstorms are one word that does not require a hyphen.

C is incorrect as herself is also a singular word. As for D, nine and days have no correlation other than it's used in the sentence. If anything, the hyphen would need to be placed between the twenty and the nine. 

Hope this helps!