To convert pounds to kilograms, you can use the conversion factor that 1 pound is approximately equal to 0.45 kilograms.
To convert 5 pounds to kilograms:
\[ 5 \text{ pounds} \times 0.45 \text{ kg/pound} = 2.25 \text{ kg} \]
Thus, 5 pounds is equivalent to 2.25 kilograms.
The correct answer is 2.25 kg.