A:①②
B:②③
C:①④
D:③④
选出与句子相符合的图片。
A. B. C. D.
(____) 1. Lily is a girl. She is my new friend.
(____) 2. He is from Shandong. He's a student..
(____) 3. Miss White is my new teacher.
(____) 4. The boy is four years old. He's from the USA.
已知三棱锥S-ABC的各顶点都在一个半径为r的球面上, 球心O在AB上,SO⊥底面ABC,AC=2r,则球的体积与三棱锥体积之比是( )