问题补充：
The teacher said that .
A. light travel much faster than sound
B. light travelled much faster than sound
C. light had travelled much faster than sound
D. light travels much faster than sound
答案：
A. light travel much faster than sound
B. light travelled much faster than sound
C. light had travelled much faster than sound
(答案→)D. light travels much faster than sound
解析：这题考查宾语从句的用法，当宾语从句的内容是客观真理时，即使主句是过去时，从句也是一般现在时，又因为主语是：light，谓语用travels。选D。
