Final answer:
Jackie's statement that m< 1 = 110 implies m< 2 = 110 can be justified because vertical angles are congruent; hence, the correct option is C. Vertical angles are congruent.
Step-by-step explanation:
Jackie said that if m< 1 = 110 then m< 2 = 110 as well. To justify Jackie's statement, we need to consider properties of angles formed by two intersecting lines. The statement that the measure of angle 1 equals the measure of angle 2 implies that these angles are related in a special way. If these two angles are not adjacent, but opposite to each other, they are vertical angles, which are congruent according to geometric principles.
Therefore, the correct justification for Jackie's statement is C. Vertical angles are congruent.