Studies suggest that there is a positive correlation between intelligence and the brain's:
a. rate of glucose consumptionb. production of endorphinsc. neural processing speedd. ability to process language in the right rather than the left hemisphere

C. neural processing speed

Explanation

Neural processing speed determine how much time a person need in order to perform a certain level of mental tasks.

When solving a complicated problems, people with higher neutral processing speed will be able to conduct and pass through several different mental process and eventually come up with a solution in a much faster rate compared to the people who have slow neural processing speed.

Because of this, researchers believe that there is a positive correlation between intelligence and neural processing speed (even though this might not be 100% the case)