Question

which microscope did robert hooke use to study tree bark?
electron microscope
compound light microscope
simple microscope
scanning microscope

Explanation:

In 1665, Robert Hooke used a compound light microscope to observe cork (tree bark). He saw small box - like structures and named them "cells". Electron microscopes and scanning microscopes were developed much later. A simple microscope has only one lens, while a compound light microscope has multiple lenses which gave Hooke a better magnification to observe the cork structure.

Answer:

compound light microscope