Answer the following question given this paragraph: 

- For lenses, the distance from the center of the lens to the focus is . Focal lengths are positive for converging lens and negative for diverging lens. The distance from the center of the lens to the object in question is , where distances to the left of the lens are positive in sign. The distance from the center of the lens to the image is . This number is positive for real images (formed to the right of the lens), and negative for virtual images (formed to the left of the lens).


Q: What lengths are positive for converging lens and negative for diverging lens?

 Choices:

- light lengths

- wavelengths

- differential lengths

- focal lengths

A:
focal lengths
