Without knowing the proportion of slaves who were allowed to get married this quote alone does not support D.
If, say, 90% of slaves were married then it does.
If, say, only 10% of slaves were married then it does not tell us much. We cannot simply assume that slave owners’ behaviour towards their unmarried slaves was the same as towards their married slaves. It is entirely possible that they were more likely to separate couples.
To really be able to answer D we also need to know the proportion of slaves who were married and the behaviour of slave owners toward their non married slaves. The data you give here is insufficient to give a definitive answer either way.