Question

16 vertical angles
a are congruent
b add up to 90 degrees
c add up to 180 degrees
d add up to 360 degrees

Explanation:

Vertical angles are formed when two lines intersect. By the vertical angles theorem, vertical angles are always congruent (equal in measure). Option B describes complementary angles (sum to 90°), option C describes supplementary angles (sum to 180°), and option D is incorrect for vertical angles.

Answer:

A. are congruent