If pieces A, B and C must be parallel, what be true <1, <2, and < 3?

What must be true is that the three angles must be equal to one another

Step-by-step explanation:

Here, we want to know what must be true of the three angles if the pieces must be parallel

What must be true of the angles is that they must be corresponding to each other

If they are corresponding, that means the angles are congruent

Given that they are congruent, it simply means that they are all equal to each other