Which of the following rules states that with the increase of every ${10}^{\circ }C$ temperature the rate of metabolic activity gets doubled?

Bergmann's rule states that species of larger size are found in colder environments and species of smaller size are found in warmer environments. 

Allen's rule states that body form is linear in warm climates and more rounded and compact in cold climates. Round body shapes give a smaller surface area to volume ratio. 

Jordon's rule states that fin ray, vertebrae or scale numbers increase with the decrease in temperature.