Answer:C) ∠ 1 and ∠ 4
Explanation:
Given: A diagonal support beam is attached to the gate of a fence.
If the top and bottom sides of the gate to be parallel , then the alternate interior angles must be congruent.[ because if two lines are parallel the alternate interior made by transversal must be congruent]
Thus, C is the right option as ∠ 1 and ∠ 4 are the only alternate interior pair given in options .