The type of lens used as a simple microscope

Simple microscope is a magnifying lens which is made up of convex lens of short focal length.

It is an instrument used to view the smaller objects by magnifying it.

Uses:

· It is used in biology to study biological specimens like insects, algae, fungi etc.

· It is used by jewelers to see fine parts of jewelry.

· It is used by watchmakers to see small parts of a watch.

· It is used to see the enlarged image of letters of a book, textures of fibers, or threads of a cloth.

Hence, the option is D, i.e. convex lens.