Nubians did not use the nile for trade because .
a.
of the cataracts
c.
they were not a mercantile society
b.
they didn’t live near the nile
d.
they didn’t know how to make boats

A, because of the cataracts.

Explanation:

The cataracts made the river too dangerous to travel in as the rock filled rapids would destroy the boat, and destroy them.

after the roman empire, the catholic church began to unify by taking on many duties of a government.

four sitting presidents have been assassinated while in office but the first was abraham lincoln,