To find the volume, you can use the formula:
\[ \text{Volume} = \frac{\text{Mass}}{\text{Density}} \]
In this case, the mass is 4 grams and the density is 2 g/mL.
Plugging in the values:
\[ \text{Volume} = \frac{4 \text{ g}}{2 \text{ g/mL}} = 2 \text{ mL} \]
So the correct response is:
2