How did developments in cartography assist European explorers?

the answer is b: the religion they practice.

here's why:

there were many different native american tribes and those with similar characteristics formed a main tribe or nation. each had its own language, religion and customs.

i believe your answer is d)

a. poison gas was sprayed over battlefields by airplanes to weaken enemy positions before major attacks.

because of the war the westeners befriended japan and each other advance.