Answer:
The lens to be used for the objective is lens A
Step-by-step explanation:
The objective of a compound microscope
The focal length of the lens used for the objective = 1/(magnification obtained)
The focal length of most modern is equal to the tube length
The range of sizes for the focal length of a microscope is between 2 mm and 40 mm
Therefore, the appropriate lens to be used for the objective of the compound is lens A that has a focal length of 0.50 cm = 5 mm