The answer is geothermal energy. This energy can be harnessed to generate electricity. The energy emanates from the deep core of the earth due to the radioactivity of the rocks in the region. The radioactivity heats Magma from the mantle which subsequently heats the rocks and fluids in the earth crust.
The correct answer is that mammals use a closed, double loop , four chambered heart as a circulatory system of the body.
The circulatory system of mammals is closed system that consists of four chambers, two articles and two ventricles. The deoxygenated blood comes into the heart from one loop and the oxygenated blood from other loop from the heart is circulated to the whole body. This is called as double circulation.
