How long were the enlistments to the Union army that Lincoln called for?

three months

Explanation:

On 15 April 1861, President Abraham Lincoln summoned 75,000 militia to serve for three months. (Oversubscribed, 91,816 were actually accepted.) Then, without legal authority, he increased the regular army by 22,714 men and called for 42,034 three‐year volunteers.

b. africa to the americas

explanation:

offline recommendation systems option b

because recommendation systems produce a list of two ways

1. through collaborative filtering

or

2. through content-based filtering