Most vacuoles in a cell store
a. sugars
b. water

Vacuoles store both water and sugars.

Explanation:

Vacuoles are multifunctional organelles found in the cells of all plants and fungi, as well as in some protist, animals and bacterial cells. Indeed, vacuoles are small compartments in the cytoplasm of the cell, however, unlike what  is observed by the human eye, these are not empty, but contain chemicals and enzymes that allow substances to degrade.

Vacuoles are made primarily of water and amino acids. Also, the fluids inside the vacuoles includes enzymes, sugars, mineral salts, oxygen, carbon dioxide and some pigments responsible for the coloring of the leaves of plants and flowers.

The vacuoles are surrounded by a layer of lipids, which allows salt water to be kept out of the cytoplasm. Vacuoles do not have a specific size or shape. These two characteristics will depend on the individual needs of the cell. The central vacuole occupies 90% of the cell volume and can reach 95% when it expands by water absorption.