发布网友 发布时间:2024-04-18 02:17
共3个回答
热心网友 时间:2024-04-19 22:39
选d at the speed 是固定搭配表示以.....的速度 the speed(at which light travels)is said to be the maximum in the universe 括号内的是定语从句 我们可以造个句 the light travels at the speed of 3000000000 meters per second 这样你就明白了吧。热心网友 时间:2024-04-19 22:40
d吧,这是个定语从句,speed是先行词,light travelS at the speed,用which代表speed,就应该是at which热心网友 时间:2024-04-19 22:45
B. by which