Answer the following question given this paragraph: 

Convex lenses are thicker in the middle than at the edges. They cause rays of light to converge, or meet, at a point called the focus (F). Convex lenses form either real or virtual images. It depends on how close an object is to the lens relative to the focus. Figure below shows how a convex lens works. You can also interact with an animated convex lens at the URL below. An example of a convex lens is a hand lens.


Q: Convex lenses are thicker in the middle than at the edges so they cause rays of light to converge, or meet, at a point called what?

 Choices:

- the center

- the base

- the apex

- focus

A:
focus
