Answer:
C. 6 units
Step-by-step explanation:
Let, the radius of the cylinder = r units.
Then, the height of the cylinder =
=
units.
Also, the volume of the cylinder is 24π cubic units.
Since, we know,
Volume of a cylinder = 
i.e. 
i.e. 
i.e. 
i.e. r= ±2
Since, the radius cannot be negative.
So, the radius is 2 units.
Then, the height of the cylinder =
= 6 units.
Hence, option C is correct.