单项选择题
In the figure above, m//n. Which of the angles are supplementary to ∠1？（）
A. ∠2 B. ∠3 C. ∠5 D. ∠6 E. ∠7
A. if Quantity A is greater; B. if Quantity B is greater; C. if the two quantities are equal; D. if you cannot determine the relationship based on the given information.
