The correct answer is option d.) vertical angles 5 and 7.
In the given diagram, line
intersects parallel lines 1 and 2, creating several pairs of angles. Let's analyze each option:
a. Same side exterior angles 2 and 7:
- These angles are always congruent. Same side exterior angles formed by a transversal cutting parallel lines are supplementary, and in this case, angles 2 and 7 are supplementary.
b. Alternate exterior angles 1 and 7:
- These angles are always congruent. Alternate exterior angles formed by a transversal cutting parallel lines are congruent, and in this case, angles 1 and 7 are congruent.
c. Corresponding angles 3 and 7:
- These angles are always congruent. Corresponding angles formed by a transversal cutting parallel lines are congruent, and in this case, angles 3 and 7 are congruent.
d. Vertical angles 5 and 7:
- These angles are not always congruent. Vertical angles formed by intersecting lines are always congruent, but angle 5 is not a vertical angle to angle 7.
The pair of angles that are not always congruent is option d. Vertical angles 5 and 7 are not always congruent.
Therefore, the correct option is d.