Please help me with science!

Can someone me with this and tell me what’s fracking and what does it have to do with carbon, carbon dioxide, or fossil fuels?

Which of the following describes a negative feedback loop? when the heart rate is too high, the body sends hormones that continually increase the heart rate higher. when a pregnant woman is in labor, the body sends hormones that increase the intensity of contractions, which then increases the secretion of the same hormones. when blood sugar is too low, the body sends hormones that raise blood sugar until it reaches a typical level and hormone secretion slows. when a person is jogging, the body sends hormones that continually decrease the rate of oxygen supply to the legs.

What are antigens and antibodies? how are they involved in the body’s response to incompatible blood?