1. Which group of people did the Romans view as a threat to the empire?

The 1st real Threat was the Etruscan league.

Explanation:

There were conflicts before that(Latin wars). But By the 4th century BC, Etruscan's had formed an Alliance with some of the Celtic Tribes to the North. Becoming a major threat to Rome

crop rotation kepy different plants in the soil instead of once constintly. when switching out plants you have different nutrients being absorbed at different speeds and different roots growing differently therfore the spoil and water flow have to adapt and carry fresh nutrients to carry the constant changes that were going on in the soil.

"the attempts of the proletariat to rise above this abasement"