What is the shape of the f-orbital ?
A. Spherical
B. Dumb bell
C. Double dumb bell
D. No definite shape

Hint: First we have to understand the basic concept of the shells and the subshells. Now we have to define the holding capacity of each subshell accordingly by defining the amount of the orbitals and electrons. This also defines the space needed hence the shape that would be obtained regarding each of the subshells. By this we will get the shape of the f-subshell.

Complete step by step answer: To understand we need to know that the shells of atoms are further divided into the subshell system where the electrons are actually found in the discrete spaces called as orbitals. They are as follows :
S-subshell: This is the first subshell in the segment where there is maximum space of $1$ orbitals and $2$ electrons. They are oriented in the shape of spherical spaces.

P-subshell: This is the second subshell in the segment where there is maximum space of $3$ orbitals and $6$ electrons. They are oriented in the shape of Dumb bell.

D-subshell: This is the third subshell in the segment where there is maximum space of $5$ orbitals and $10$ electrons. They are oriented in the shape of Double Dumb bell.

F-subshell: This is the fourth subshell in the segment where there is maximum space of $7$ orbitals and $14$ electrons. There is no discrete shape in the f-subshell. This is because of the complexity of its nature.
Therefore the answer would be option D, No definite shape.

Note: Although we generally study uptil the f-subshell but that doesn't mean that it is the last subshell. Though in the current scenario of discovered elements no element exceeds the capacity till the f-subshell but they exist further too.