单选题 Astronauts receive extensive training to prepare themselves both physically and psychologically for complexity and rigor of a space mission.

【正确答案】 D

【答案解析】答案：D. for complexity: for the complexity 分析：the AAAAA of BBBBB 的结构，定冠词不能省略。参考译文：宇航员为了适应复杂的高要求的空间任务，接受广泛的体能和心理的训练。