Ms. Zhou Mr. Li is humorous. They are popular among us students.
A:Both;and
B:Neither;nor
C: Either;or
D:Not only;but also
探照灯反射镜的纵断面是抛物线的一部分,光源在抛物线的焦点,已知灯口直径是60 cm,灯深40 cm,则光源到反射镜顶点的距离是____ cm
地球除了人类还有近3000万—5000万种生命物质,这说明( )