Which structure protects microorganisms in unfavorable environments?

The structure that protects microorganisms in unfavorable environments is a cyst. Cysts are dormant forms that some microorganisms can form in response to harsh conditions, such as extreme temperatures, lack of moisture, or limited food supply. By encasing themselves in a protective coating, microorganisms can significantly enhance their chances of survival until conditions improve. The cyst's tough exterior helps prevent desiccation and shields the organism from environmental stressors, making it an essential survival mechanism for many protozoa, bacteria, and algae.

The other structures mentioned serve different functions. Earspots are not relevant in this context, as they generally pertain to sensory functions and do not provide protection. Pseudopodia are extensions of the cell used for movement and feeding, but they do not provide the protective mechanism that cysts do. A pellicle is a flexible outer covering found in some protists, but it primarily offers structural support and does not provide the same level of protection during unfavorable conditions as a cyst does.