Answer : The correct statement is, They are vertical angles.
Step-by-step explanation :
Complementary angles : It is defined as the angles that has the sum of 90°.
Supplementary angles : It is defined as the angles that has the sum of 180°.
Adjacent angles : It is defined as they have a common side and a common vertex.
Vertical angles : It is defined as the pairs of opposite angles made by two intersecting lines.
From the given figure, we conclude that the ∠3 and ∠6 are vertical angles.
Hence, the correct statement is, They are vertical angles.