Final answer:
Magnesium is an important mineral ion that stabilizes the cell membrane and supports ribosome function, while potassium is also essential for protein biosynthesis by ribosomes. The correct option is c.
Step-by-step explanation:
An important mineral ion that stabilizes the cell membrane and contributes to ribosome function is magnesium. Magnesium ions play multiple roles in organisms, such as being part of the chlorophyll molecule in plants and it is also involved in many biochemical reactions within cells.
For example, magnesium is critical for the photosynthetic process in plants and is required by heterotrophs as a dissolved cation in the cytosol. In addition, potassium, another important mineral ion, is essential for various metabolic functions including protein biosynthesis by ribosomes, acting as a major cation inside the cell.
Therefore, the correct option is c.