Sorry If I'm wrong, but I'm pretty sure it's D.
Answer:
I think the answer is positive feedback is used to build more contractions
Answer:
A. high tide (A, C)
Explanation:
High tides on points A & C occur when the moon, the Earth, and the Sun are all lined up.
<em>SUN -----<<< EARTH >>> --- </em>
<em> ----MOON</em>
<em>( as accurate as it can be in 2D)</em>
As you can see, they are all in a straight line. The gravity of both the moon and the Sun are combined to output the greatest amount of gravitational force as possible; creating high tides on the 2 sides of the Earth. Points A & C represent these two sides and are therefore the answer.