Please help. I don't get this

Determine the maximum r-value of the polar equation r =3+3 cos 0

Apebble is thrown into a calm lake, ripples are formed from the center and move outward. the water particles in the lake travel in a circular pattern that moves up and down on the surface of a lake, and the energy travels a) diagonally. b) downward. c) horizontally. d) upward.

What are the similarities & differences between a thermistor and a light dependent resistor in physics?