What is basal metabolic rate?

the rate at which the heart pumps blood

the rate at which someone eats

the breathing rate during physical activity

the rate at which energy is used when the body is at rest

Explanation:

1. Even when our body is at rest, it's not a myth that it's burning calories by processing all the nutrients in our body, by breathing, by production of cells, etc. So, BMR is a number of calories one's body needs in order to function. There is a BMR if we want to gain, maintain, lose weight. It's different for each and every individual as it depends on lifestyle, height and weight.

2. If a person is at rest, it's usually some number between 60 and 70 hear beats per minute. It's normal that heart is pumping more blood if it's in any kind of action, especially when exercising, as our muscles need more oxygen.  3. Amount of calories depend on every individual. It's important to have a balanced diet and exercising as addition to the whole package. As said earlier, the BMR depends on our goals, and on our height and weight, as well as the lifestyle we lead, and if we are suffering from any condition or disease.

4. It depends on the type of physical activity. If we are talking about intensive ones, like weight lifting, it can go from 15 breaths per minute to, 40-50 really fast. We measure the breathes we take in by volume of oxygen uptake.

5. Usually, women should eat around 1400 kcal per day, a men should eat around 1800kcal. Naturally, it depends on one's build, lifestyle, exercise level, weight, height, etc. Body is burning calories and produces energy at rest around 60% out of the whole amount. They way calories are burned in someone's body, depends on the size and condition of the body.

answer(b) keep oxygenated and deoxygenated blood separate;