Question

which characteristic is given by the angular momentum quantum number?
orbital size
orbital mass
orbital shape
orbital orientation

Explanation:

The angular - momentum quantum number ($l$) determines the orbital shape. For example, $l = 0$ is an s - orbital (spherical shape), $l=1$ is a p - orbital (dumb - bell shape). It has nothing to do with orbital size (determined by the principal quantum number $n$), orbital mass (not a relevant concept in this context), or orbital orientation (determined by the magnetic quantum number $m_l$).

Answer:

orbital shape