1. The problem asks to identify which sides of triangle $\triangle ABC$ are legs and which are the hypotenuse. 2. In a right triangle, the hypotenuse is the side opposite the right angle and is the longest side. 3. The legs are the two sides that form the right angle. 4. Given the triangle with vertices $A$ at lower-left, $C$ at lower-right, and $B$ at the top, the right angle is at $C$ (since $B$ is at the top and $A$ and $C$ are at the bottom). 5. Therefore, the legs are $AC$ and $BC$, and the hypotenuse is $AB$. 6. So, the correct statements are: - $AC$ is a leg of $\triangle ABC$. - $BC$ is a leg of $\triangle ABC$. - $AB$ is the hypotenuse of $\triangle ABC$. 7. The incorrect statements are: - $AB$ is a leg of $\triangle ABC$ (false). - $AC$ is the hypotenuse of $\triangle ABC$ (false).