Question

Which pair of angles are alternate interior angles?

Answer 1

we know that

Alternate interior angles are two interior angles which lie on different parallel lines and on opposite sides of a transversal. Alternate interior angles are congruent

see the attached figure with letters to better understand the problem

in this problem

the parallel lines are the lines a and b

the transversal line is the line c

so

the alternate interior angles are the Angle $3$ and Angle $6$

m∠3=m∠6

therefore

the answer is the option

Angle $3$ and Angle $6$

Answer 2

Ângulos alternos internos: 
3 e 6