Final answer:
The Massachusetts fair housing laws prohibit discrimination in housing based on certain protected classes, but religious beliefs are generally considered a permissible basis for discrimination in housing rentals.
Step-by-step explanation:
The correct answer is d. refusing to rent to an unmarried could on religious grounds. The Massachusetts fair housing regulations prohibit discrimination in housing based on certain protected classes, such as age, disability, and source of income.
However, religious beliefs are generally considered a permissible basis for discrimination when it comes to housing rentals. While refusing to rent to someone based on their age, disability, or participation in a housing subsidy program is illegal, refusing to rent to an unmarried couple on religious grounds is allowed under Massachusetts fair housing laws.