Lactic acid buildup when you’re exercising causes a build up of oxygen. Your body cannot break down glucose in the blood. So, your heart beat increases because there is more oxygen than normal needing to be pumped throughout the body.
In short terms: because your heart needs to pump more oxygen, it is pumping faster causing a faster heart rate.
This is just a guess but Florida is very humid, so I think the humidity would cause late afternoon thunderstorms.
Second one:
Antigens trigger the production of antibodies and antibodies destroy pathogens
The answer should be option B and C "It contains 46 chromosomes, Each strand contains chromosomes from one parent." When a baby is made it receives 24 chromosomes from the mother and 24 chromosomes from the father in equal will have 46 chromosomes. It's also true that each strand contains chromosomes from one of the parents.
Hope this helps.