Why did slavery grow in the south but die out in the north?

Slaves are mostly use to tend the plantation. The South need more slaves when the amount of plantation increased as time pass. The North turn to factory as time pass which mean less slaves is needed.

offline recommendation systems option b

because recommendation systems produce a list of two ways

1. through collaborative filtering

or

2. through content-based filtering

worldwide, 780 million people do not have access to an improved water source. an estimated 2.5 billion people lack access to improved sanitation (more than 35% of the world's population)