单项选择题
There could be life on the Mars in the future if （）.
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
单项选择题 Some scientists think there may have been life on the Mars in the past because （）.
单项选择题 （1）处应填写（）
问答题 After a busy day of work and play, the body needs to rest.
