A、
Its ability to launch a spacecraft to Mars.
B、
Its ability to land a spacecraft on Mars.
C、
Its ability to launch a manned space flight to Mars.
D、
Its ability to land a spacecraft on earth safely.
【正确答案】
B
【答案解析】
A、
In 2018.
B、
In 2019.
C、
In 2017.
D、
In 2020.
【正确答案】
D
【答案解析】
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