案例分析题 People may be able to live on the Mars ______.

A．it supported life in the past
B．certain gases are used to cool the planet
C．the atmosphere can be heated enough to grow simple plants
D．the planet’s volcanoes become as active as they were in the past

A．there is no life there now
B．there is a large amount of water at the poles
C．the Mars may be able to support life in the future
D．conditions may have been similar to those on the Earth