And were disgruntled over moses’ marriage and ministerial supremacy and challenged his divinely given authority.

a. joshua and caleb
b. aaron and miriam
c. kadesh and barnea
d. balaam and balak

b. Aaron and Miriam.

Explanation:

In the book of Numbers, we see Moses was questioned and his authority was also put in question by his own siblings, Aaron and Miriam (Numbers 12). Moses had taught the Israelites to not intermarry with the foreigners (Deuteronomy 7:3) among them but he himself married one (Numbers 12:1). So, they took upon themselves to be leaders of the people. But God's "anger was kindled against them" (Numbers 12:9) and he inflicted Miriam with leprosy to the brink of dying. Only after Aaron intervened to Moses to forgive them did God remove it. This brings to the point to never question God's appointed leaders and to always respect them.

the structure was most likely used for;

c. playing a ball game with stone hoops