题目

Film cameras and digital cameras work in a similar way. Film cameras After all, a film camera is basically a light – proof (不透光的) box. It has a lens (镜头) system to focus light onto the film at the back of the camera. Let’s suppose that we are outside on a beautiful summer day trying to take a picture of the family dog. We are using a film camera. We finally get the dog to lie still. You point the camera at him. What happens? Light goes into the camera lens and hits the shutter. In other words, nothing happens yet. Now let’s say that the dog looks really cute and you decide 苹果的甜味来自（　　）A．植物吸收的糖分B．细胞液中的糖分C．细胞壁的糖分D．果实中的糖分