The correct answer is C. Chloroplast.

Chloroplasts are organelles found in plant cells and some algae, responsible for photosynthesis. During photosynthesis, chloroplasts convert light energy, carbon dioxide, and water into glucose (a simple sugar) and oxygen:

  6 CO\(_2\) + 6 H\(_2\)O + light energy → C\(_6\)H\(_{12}\)O\(_6\) (glucose) + 6 O\(_2\)

The other options are not correct:

A. Vacuoles are storage organelles that can contain water, salts, and other substances, but they are not involved in producing simple sugars.

B. Cytoplasm is the region between the cell membrane and the nucleus, where many metabolic processes occur. However, simple sugar production through photosynthesis occurs specifically in chloroplasts.

D. The cell wall is a structural layer outside the cell membrane that provides support and protection. It is not involved in producing simple sugars.