Sandra pushed a wooden block and it slid across the floor. The wooden block gradually slowed down and
stopped after moving 10 meters. Why did the block stop
moving?

low freq = 100 mhz

low wavelength =101.7m

length = 3x10^8/freq

see earlier

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.