A. Look!The ducks are swimming in the river.
B. The boy is crying.
C. My father took many photos yesterday.
D. Xiaoqiang is sending an email to his cousin.
E. The boy looks hungry.
____
各种建筑物都有一定的结构:体育馆是____结构;桥墩是____结构;埃菲尔铁塔是____结构。
Whoever leaves the room last must make sure________all the windows are shut.