Question

If two lines intersect, then the vertical angles formed must be

both acute angles
both equal in measure
complementary angles

Answer 1

vertically opposite angles congruent. Hence "both equal in measure"

Answer 2

When two lines intersect, they form four angles. Angles that are not adjacent (i.e., do not share a common side) are called vertical angles and these angles are congruent (or equal in measurement).