In which month does kano nigeria receive the most rainfall

Drastic boundary changes can occur for all of the following reasons except for a. a shift in the way a river flows b. the collapse of a government system c. a conflict between two neighboring groups d. one country's decision to sell land to another country select the best answer from the choices provide

Can someone me? i need to have this done as soon as possible! i'm putting 20 points on this!

Zac wanted to determine the measure of r and of ? r in the triangle below. to fine the measure of r, zac sets up the problem.42^2 + 24^2 = r 2. determine whether zac set the problem up correctly.