Which cell organelle is responsible for storing water

Correct answer is vacuole . 

Explanation : Filling this space is an organelle called a central vacuole which is full of water. Bounded by a single membrane, this organelle functions as a combination of reservoir, waste dump, storage region and even as a means of keeping the cell in shape. 

The main function of vacuoles is to hold various substances and molecules; they basically act like the storage unit of the cell. Below are some key vacuole functions, many of which relate to storing materials that the cell will need later on or which can damage the cell and therefore need to be removed:

• Remove and store waste produced during autophagy (when part of the cell is broken down due to age or damage)
• Remove and store harmful foreign products so they don’t damage the cell
• Store water
• Store nutrients such as lipids, proteins, and carbohydrates .