PLEASE THIS IS URGENT What was the size of the Roman Empire at it's height?

At its height in 117 AD, the Roman Empire was massive. It encompassed a land area of roughly five million square kilometers and ruled over somewhere between fifty-five and sixty million inhabitants

5 million square kilometres.

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