—Look, what an old palace! It looks so great!
—Yeah, it _______ nearly 800 years ago.
A：was building
B：was built
C：has built
D：is built
—About 1,200 kilometers away. But I'm not sure.
多音字注音并组词。
着：____ ____ 兴：____ ____
________ ________
实数x,y满足条件{x≥2x+y≤4-2x+y+5≥0则该目标函数z=3x+y的最大值为 ( )
