Saturatedunsaturated fats remain in liquid form at room temperature

Unsaturated fat

Saturated fats are solid at room temperature while unsaturated fats are liquid at room temperature. This is because these two kinds of fats differ in their chemical structure. Saturated fats do not have double bonds between the molecules which means there are no gaps and the fat is saturated with hydrogen molecules. Because there are no gaps, these fats tend to pack more closely together. Unsaturated fats have double bonds which break up the chain of hydrogen molecules and create gaps allowing them to pack loosely and can thus liquefy at room temperature.

B. When oxygen levels in the blood decrease, the respiratory center sends signals to the diaphragm to increase the rate at which it contracts and relaxes.

Explanation:

According to the given situation, as it is already mentioned that Robert runs before going home from school. This physical activity is likely to increase the breathing rate. The increase in breathing rate is likely to increase the demand of oxygen in the body. With the decrease in concentration of the oxygen in the blood the respiratory system in the body will get activated. The respiratory system will send signals to the diaphragm below the lungs to expand and contract at a faster rate so as to admit more amount of oxygenated air and distribute it at a faster rate.