如图,A、B、C三点在⊙O上,∠AOB=80º,则∠ACB的大小()
A:40º
B:60º
C:80º
D:100º
下列各种现象中,属于山区常见的自然灾害的是( )
Let's go to the zoo together.
—What will you do tomorrow?
—I will____.