1. He sent letter to his friends.

(-) He didn't send letter to his friends.

(?) Did he send letter to his friends?

2. My brother spent his summer holiday on the farm.

(-) My brother didn't spend his summer holiday on the farm.

(?) Did your brother spend his summer holiday on the farm?

3. The children wash their hands before meals.

(-) The children didn't wash their hands before meals.

(?) Did the children wash their hands before meals?

4. They will come there tomorrow.

(-) They won't come there tomorrow.

(?)  Will they come there tomorrow? 

5. The people were friendly.

(-) The people weren't friendly.

(?) Were the people friendly?

6. I decorated the color lights on the Christmas tree.

(-) I didn't decorate the color lights on the Christmas tree.

(?)  Did you decorate the color lights on the Christmas tree?

7. Hoa likes her new skirt.

(-) Hoa doesn't like her new skirt.

(?) Does Hoa like her new skirt? 

8. Liz injoyed her summer vacation last year.

(-) Liz didn't enjoy her summer vacation last year,

(?) Did Liz enjoy her summer vacation last year?