Answer : The correct option is 'X' (mitochondria).
Explanation :
In the given animal cell diagram,
W represent the vacuole.
X represent the mitochondria.
Y represent the nucleolus.
Z represent the cytoplasm.
The function of vacuole, it stores waste products and balance the pH level of the cell.
The function of mitochondria, most of the respiration reaction occurs in which carbon dioxide is produced by utilizing oxygen.
The function of nucleolus, it contains the hereditary information.
The function of cytoplasm, most of the chemical reaction occurs.
Therefore, the correct answer is 'X' (mitochondria).