Why did slave owners use violence against slaves?

Slavery was a very harsh system. Slaves were forced to work, without pay often doing tasks requiring very hard labor. Although many enslaved Tennesseans worked on farms, others labored in iron foundries or other businesses.  

 Slaves had few legal rights. For example, slave marriages were not recognized by law. Owners had the right to sell slaves whenever they wanted regardless of family relationships. Children could be sold away from their parents.

answer:

d. because dr. laguardia selected a widely used measure, his study generalizes to has strong external validity. external validity has limited external validity. other applications of this measure.

the widely used measure that he applied to his experiment was the benton facial recognition test. it employed on to football players and as result, only players who suffered brain concussions did not pas this test. and although it has an external validity, it is limited because it isn't general to apply to other population.

the first two-party system consisted of the federalist party, who supported the ratification of the constitution, and the democratic-republican party or the anti-administration party (anti-federalists), who opposed the powerful central government, among others, that the constitution established when it took effect in