Remember that in a triangle ABC, the angle A is opposite to the side BC, as well as the angle B is opposite to the side AC and the angle C is opposite to the side AC, as shown:
On the other hand, remember that larger sides are opposite to larger angles.
Write the sides AB, BC and CA in order from largest to smallest. Given that:
[tex]\begin{gathered} AB=16 \\ \\ BC=20 \\ \\ CA=17 \end{gathered}[/tex]
Then, the list of sides from largest to smallest is: BC, CA, AB.
Their respective opposite angles are A, B, C.
Therefore, the correct choice is option B)
[tex]\angle A,\angle B,\angle C[/tex]
