The correct answer is option c. Illegal. In 1960 there were a dozen U.S States that made interracial marriages illegal. These States were: Arizona, Colorado, California, Idaho, Montana, Maryland, Indiana, North Dakota, Nevada, Nebraska, South Dakota, Oregon, Wyoming and Utah.
In 1967, the United Supreme Court, taking the case of Loving vs Virginia as a precedent, declared the decision to make unconstitutional all laws that banned interracial marriage.