Altitudes of a Triangle

A triangle has _____ altitudes. $\left(1/ 2/ 3\right)$

For the following triangle, does the altitude lie in the exterior of the triangle, if drawn from the marked vertex.

For the following triangle, does the altitude lie in the exterior of the triangle, if drawn from the marked vertex.

For the following triangle, does the altitude lie in the exterior of the triangle, if drawn from the marked vertex.

$∆ABC$ is a right-angled triangle in which $\angle C=90°$. Name one altitude of $∆ABC$.