What type of microscope is used to see the external surfaces of cells to determine morphology?

The SEM (Scanning Electron Microscope).

Explanation
The SEM produces images of the surface shape, composition and structure (morphology) of cells by scanning the sample with focused electron beams.

The interaction between the electrons and atoms in the cell produce visual images that reveal the surface composition and structure of the cell.

The SEM can achieve resolutions at the nanometer level. The specimen or sample is usually observed in a vacuum environment.

C) to ensure each new cell has an exact copy of the dna