In the provided image, the problem asks for the side opposite to angle $\angle A$ in the given right triangle.

From the diagram:

• The right triangle has three sides labeled $a$, $b$, and $c$.
• The angle $\angle A$ is located at vertex $A$.
• The side opposite to $\angle A$ is the side across from this angle, which is labeled as $b$.

Thus, the correct answer to the question "What is the side opposite $\angle A$?" is:

$b$.

Would you like more details, or do you have any questions? Here are some related questions that may help:

1. How can we identify the side opposite a specific angle in any right triangle?
2. What is the significance of the hypotenuse in right triangles?
3. How does the Pythagorean theorem relate the sides of a right triangle?
4. What is the difference between adjacent and opposite sides in trigonometry?
5. Can you apply sine, cosine, or tangent to find missing angles or sides?

Tip: The side opposite an angle in a right triangle is always the one that does not form part of that angle itself!