C human selection is the answer hope this helps
When air is heated up the molecules spread out and move faster, so heat rises because it is less dense than the cooler air around it.
Answer:
A
Explanation:
Because there are two DNA strands in the DNA molecule and they both rotate around each other in a helix formation. So two helixes = double helix.
Food chains model energy flow through an ecosystem. Producers pump energy into an ecosystem from an environmental source, and this energy is then passed from one organism to the next.
