单项选择题

The "canals" on Mars have proved to be （）according to the passage.

A．the minor geologic characteristic of Mars
B．natural valleys on the surface of Mars
C．rivers that have kept flowing since ancient times
D．a system that irrigates the whole surface

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热门试题

单项选择题

Athletic activities are designed （）

A．to make boys stronger
B．to teach students winning spirit
C．to develop students' social and political skills
D．to improve the academic programs

单项选择题

Grandpa: Robbie, we'll go fishing soon, and we'll take your dad with us.Grandson: I'm ready, Grandpa. （）

A．You name the day
B．Enjoy yourselves
C．You can't miss it
D．Take your time