He decided to buy some  chocolate kept in an________container for his father, a_______ watch for his mother and a doll with _______for his little sister.

A. tight air; proof water; white snow    

B. air-tighted; water-proofed; snow-whited

C. tight aired; proof watered; white snowed 

D. air-tight; water-proof; snow-white

Cho 1 Ankađien X + brom(dd) → 1,4-đibrom-2-metylbut-2-en. Vậy X là

A. 2-metylbuta-1,3-đien

B. 3-metylbuta-1,3-đien

C. 2-metylpenta-1,3-đien

D. 3-metylpenta-1,3-đien