1. The problem asks to identify which sides are legs and which are the hypotenuse in triangle $\triangle ABC$ with vertices $A$ at the left bottom, $B$ at the top, and $C$ at the right bottom. 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. Since $A$ and $C$ are at the bottom and $B$ is at the top, the right angle is at $C$ or $A$ depending on the triangle orientation. Given the typical labeling, the hypotenuse is the side opposite the right angle, which is $AB$. 5. Therefore, $AC$ and $BC$ are the legs, and $AB$ is the hypotenuse. 6. Correct statements: - $AC$ is a leg of $\triangle ABC$. - $BC$ is a leg of $\triangle ABC$. - $AB$ is a leg of $\triangle ABC$ is incorrect. - $AC$ is the hypotenuse of $\triangle ABC$ is incorrect. - $AB$ is the hypotenuse of $\triangle ABC$ is correct.