VOA慢速英语:Mars: How Will Humans Get There?

短语讲解：

1. It takes only three days to get there, and three to come back.

come back 回来; 记起; 强烈反驳
例句：It doesn't matter when you'll come back.
你什么时候回来都没关系。

2. People asked him about his plan to send up to one million people to the Red Planet sometime in the next 40 to 100 years.

send up 发射; 使向上升; 毁坏
例句：Please send up a boy to help me with my luggage.
请派一位服务生上来帮我拿行李。