“slaves are in the power of masters, a power derived from the law of nations: for among all nations it may be remarked that masters have the power of life and death over their slaves, and that everything acquired by the slave is acquired for the master.
but at the present day none of our subjects may use unrestrained violence towards their slaves, except for a reason recognized by law. for, by a constitutio of the emperor antoninus pius, he who without any reason kills his own slave is to be punished equally with one who has killed the slave of another.”
—the institutes, book i, chapter viii
according to the above law, which of the following statements is true?

violence towards slaves was not tolerated under any circumstances.
masters were allowed to kill their own slaves, if they had a reason for doing so.
masters were allowed to kill another master’s slaves, if they had a reason for doing so.
slaves had legal rights to keep their earnings for themselves.