—Who ______ it be that is singing in the next room?
—It _______ be Lucy, but I am not sure.
A.can ; may B.may ; can C.can; must D.must; may
—Who ______ it be that is singing in the next room?
—It _______ be Lucy, but I am not sure.
A.can ; may B.may ; can C.can; must D.must; may
A