The correct option is B Increase in optimum temperature increases the rate of respiration
Respiration is an enzyme controlled process. Enzymes get denatured i.e., hydrogen bonds get broken down in the enzymes at high temperatures. Thus, at high temperatures the respiration rate decreases.
The temperature at which the enzyme is most efficient is called as the enzyme's optimum temperature. Thus an increase in optimum temperature would result in increase in the rate of respiration.