imc

Drawing the tetrahedron out and testing side lengths, we realize that the $△ACD,△ABC,$ and $△ABD$ are right triangles by the Converse of the Pythagorean Theorem. It is now easy to calculate the volume of the tetrahedron using the formula for the volume of a pyramid. If we take $△ADC$ as the base, then $\overline{AB}$ must be the altitude. The volume of tetrahedron $ABCD$ is $\frac{1}{3}\cdot \frac{3\cdot 4}{2}\cdot 2=\boxed{4}.$