单项选择题

A
根据下面短文回答下列问题。
When a group of women got on the bus, every seat was already taken. The conductor(售票员) found a man who seemed to be asleep (睡着了) o Fearing (担心) that the man might miss his stop, he called the man: "Wake up(醒一醒)!"
"I was not asleep," the man said. "Not asleep But you had your eyes closed," the conductor said. "I know. I just don’t want to look at ladies(女士们) standing up in a crowded(拥挤的) bus.\
The man closed his eyes, because ______.