To stop any ofter wars form happening in Europe.
Most of the heat is refracted on the waters surface.
The tilt of the Earths axis can affect where the Suns rays hit the Earth. If the northern hemisphere tilts slightly more than the southern hemisphere, the northern hemisphere is facing the sun more often, this is known as "Summer" for people in the north, and "Winter" for people in the south. Im not sure if that answered your question, but the suns rays bounce off the Earths surface and clouds and sometimes hit each other in our atmosphere.
You didn't give your choices but sin 21 equals 0.358.
The reason is that current methods used to “calibrate” models often render them inaccurate. That's what Jonathan Carter stumbled on in his study of geophysical models.
If you want a more detailed explanation here’s a explanation from quizlet.