Barb (35) is divorced from Dan (40). They are the parents of Boyd (12). Boyd lives with his mother, Barb, who pays over half the cost of maintaining the home. The divorce decree gives Dan the unconditional right to claim the dependency exemption for Boyd. Boyd meets all of the tests for dependency for Barb as a qualifying child. Barb's most advantageous filing status is __________.

Head of household.

Married filing jointly.

Married filing separately.

Single.