一般过去时与现在完成时对比 — 英语选择题

On Mars, a person must wear a special suit that supplies air and protects the bo…

For this test, a rover can move only when it has power. The rover is moving. Whi…

用所给动词的适当形式填空：More space stations ______ (build) on Mar…

In the future, humans may live on Mars. Because the gravity on Mars is much weak…

People use robots to study Mars. Choose the sentence with the same meaning. A. R…

—Tom asked the robot what it could do to help with the housework. The robot re…