Answer:
Compound light microscope
Explanation:
This is the ideal microscope because it requires the passage of harmless beam of light through the specimen.Since the pond contain living creatures this is best to use.
C and D both require the transmission of beam of electrons through a sample. D depends on the reflection of the electron after scanning the specimen surfaces and sent this to the lenses of the observer.(C)involved the passing of the beam of electrons through the specimen the interaction of the electrons with the atoms in the specimen(,therefore in both cases these specimens can not be wet and living.
The specimen should be dry in both cases and therefore non -living ,because the chamber for the specimen must be a vacuum,and living organism can not survive in the vacuum. Thus pond water can not be used as specimen because the specimen in the water but me be living.