<span>The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and 99% of its water vapour and aerosols. The average depth of the troposphere is approximately 17 km in the middle latitudes. It is deeper in the tropics, up to 20 km, and shallower near the polar regions, approximately 7 km in winter. The lowest part of the troposphere, where friction with the Earth's surface influences air flow, is the planetary boundary layer. This layer is typically a few hundred meters to 2 km deep depending on the landform and time of day. The border between the troposphere and stratosphere, called the tropopause, is a temperature inversion.</span>
I'm pretty sure it would be D, since
Blood flow to the heart via the following vessels:
1. superior vena cava
2. inferior vena cava
4. coronary veins/sinus
Animals storing energy is a long term cause when an animal is wanting another animal their is things that do change in their bodies and it can cause them to do theses kinds of things .