What are lysosomes primarily responsible for?

Lysosomes are primarily responsible for digesting certain materials within the cell, making option C the correct choice. These organelles contain a variety of enzymes that break down macromolecules, such as proteins, lipids, carbohydrates, and nucleic acids, into their smaller components. This process is essential for cellular maintenance and recycling, allowing the cell to dispose of waste material and cellular debris effectively.

Lysosomes play a crucial role in autophagy, a process in which cells degrade their own components to maintain homeostasis, especially under conditions of nutrient deprivation. By breaking down damaged or surplus cellular components, lysosomes contribute to cellular health and function.

The other choices represent functions of different organelles or processes within the cell. For instance, synthesizing proteins is primarily the function of ribosomes and the rough endoplasmic reticulum. Storing lipids is associated with other structures like lipid droplets or cells specializing in fat storage, such as adipocytes. Transporting substances across the membrane typically involves membrane proteins or vesicles, not lysosomes directly. Therefore, lysosomes' specific role in digestion distinctly supports the correctness of option C.