What makes our metabolism faster and what slows it down?

When someone tries to lose weight and he/she does a lot of exercise and eats healthy food, but that does not have results, the reason is slow metabolism. One of the most important things for good metabolism is to drink a lot of water (cold water is better for metabolism than warm). It is also important to have at least three meals during the day, and not to eat after dinner. It means that, if you eat after 18 or 19h, it will have bad effect on your metabolism and health. Good sleep is also important for metabolism: you should go to sleep around 22 or 23h. Stress is also one of the things which slows our metabolism...

Ithink the correct answer is c