Not all areas on earth's surface receive the same amount of radiation because earth's surface
a. is flat
b, is curved
c. has continents on it d, is mostly water.

We all know that its not a since obviously the earth is not flat so the more appropriate answer would b since it is  curved and the sun doesnt get to reach all areas of the earth because it is tilted on its axis 

Ihaven't done that yet, so no idea,but this is not the right place to ask

Then it is june the conclusion to the second sentence is just restating "if it is june then it is summer"