Explanation:

Initially, let's establish the structure of all compounds to determine which ones are chiral.

(a)

        
H
|
C - C - C - C - Br
|
H
        
    

(b)

        
Br
|
C - C - C - C - Br
|
H
        
    

(c)

        
Br   Br
  |   |
C - C - C - C
        
    

(d)

        
Br
|
C - C - C - C
|
H
        
    

Now, we can observe that 2-Bromobutane has a chiral carbon (a carbon with four different attachments).

Therefore, it is a chiral molecule.