Vertical angles must check all that apply

The correct options are:

B.  Have the same vertex.

C.  be congruent.

Step-by-step explanation:

Vertical Angles--

These are formed by the intersection of two lines.When two lines intersect then four angles are formed such that each pair of the opposite angles are called vertical angles.The vertical angles have a common vertex.Since, one vertex is obtained when the lines intersect.They could never be adjacent angles.Also, they may be obtuse, acute or right angles.The  measure of each of the vertical angles are always  equal i.e. the angles are congruent.

A= b/2 because u simplying both sides of equation