Answer:
Option (a).
Explanation:
Mitochondria are double-membrane bound, present in almost every eukaryotic cells. They provide site for the cellular respiration that produces ATP as energy molecules, and hence, are known as power house of the cell.
Inner membrane of mitochondria have many finger-like projections or folds, known as cristae that leads to an increase in surface area of inner membrane.
As ATP synthesis takes place on inner membrane of mitochondria, increased folding provides more surface area or space for ATP production.
Thus, the correct answer is option (a).
