The correct answer is C. 0.6 F.
The capacitance of a capacitor is defined as the ratio of the charge stored on it to the voltage across it. In this case, the capacitor stores 0.24 coulombs of charge at a voltage of 10 volts. Therefore, its capacitance is $C = \frac{Q}{V} = \frac{0.24 \text{ C}}{10 \text{ V}} = 0.24 \text{ F}$.
Option A is incorrect because it is the capacitance of a capacitor that stores 0.024 coulombs of charge at a voltage of 10 volts. Option B is incorrect because it is the capacitance of a capacitor that stores 0.12 coulombs of charge at a voltage of 10 volts. Option D is incorrect because it is the capacitance of a capacitor that stores 0.8 coulombs of charge at a voltage of 10 volts.