B. Why are the resources listed in part (a) considered "renewable"?

I would need to see the part a to be more specific but this may help:

resources like solar, water, wind are considered renewable because they will never run out, they can be replenished over and over again. There will always be a sun (and if there wasn't then we'd have bigger conserns than renewable energy) and the wind will always blow. It can never run out because you use too much unlike coal and fossil fuels.

Hope this helps!

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.

blue light is scattered in different directions by the tiny molecules of air. blue is scattered more than other colours because it has a shorter distance to travel which results in smaller waves. this is why we see a blue sky most of the time.