单项选择题

The final goal of designing a lens is______.

A．to trap the opponent's lenses
B．to focus light with lenses
C．to hand-make lenses at low cost
D．to reflect light by means of curved surfaces
<上一题 目录 下一题>
热门 试题

单项选择题
The stages of sleep take on______.
A．an irregular aspect
B．a regular aspect
C．a punctual aspect
D．a similar aspect
单项选择题
The brain waves are the slowest during______.
A．stage 1
B．stage 2 and stage 3
C．stage 4
D．REM sleep
相关试题