Physics - Vectors-- Could you help me please?

Identify the amplitude on the diagram and give the correct description. question 3 options: a because amplitude is the distance from wave crest to wave crest. b because the wavelength shows amplitude. c because amplitude is the distance between a crest (or trough) and rest. d because wavelength show amplitude. (brainiest if you get it right! ) ~kayla

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

What is special about a dc circuit ?