Final answer:
A microscope should be covered to prevent dust from collecting on lenses, ensuring clear images and protecting its delicate parts.
Step-by-step explanation:
You should keep a microscope covered to prevent dust and debris from accumulating on the lenses. Dust and debris can degrade the magnification quality by interfering with the precision of light refraction through the lenses. Since the lenses are key components for achieving the necessary magnification, it is crucial to maintain their cleanliness for the microscope's optimal performance. Covering the microscope also protects its delicate parts from potential damage that can occur if left exposed.