What is the purpose of the pericardial sac that surrounds the heart in mammals

Pericardial sac has protective tole

Explanation:

Pericardial sac or pericardium is a fibrous tissue that surrounds the heart. It has two coats:

the outter coat-parietal pericardiumthe inner coat-visceral pericardium or epicardium which is double-layered and contains pericardial fluid between those two layers (pericardial fluid is necessary as a lubricant for the heart movement).

Besides lubrication, percardium also protects heart from infections, fixes it and limits its movements.

We can use solar powered cars or ride bikes instead of cars that burn fossil fuels

Idon't know how to do this but maybe ask your mom or dad