在与异性相处时，我们要学会保护自己，而对自己最好的保护来自   [ ]

A、社会法律和道德

B、学校的纪律和规则

C、良好的生活习惯

D、自我保护意识和自律

68 It was at four o'clock in the afternoon ____ he and his grandpa reached the museum in Guanghan.

A．while

B．that

C．when

D．As