题目内容：

What is a mouse --It's something that is used ( )pointing at different parts of screen.
A to B by C for D with

优质解答

选A...题目“--什么是鼠标呢?”“--是用来指向（电脑）屏幕不同位置的东西.” be used to doing为“用来做..”的短语,其中的to为介词,to后动词加ing.