Final answer:
The density of the sample with a mass of 25 g and a volume of 2.8 ml is 8.93 g/ml.
Step-by-step explanation:
The density of a substance can be calculated by dividing the mass of the substance by its volume. In this case, the mass of the sample is 25 g and the volume is 2.8 ml.
To find the density, divide the mass by the volume: 25 g / 2.8 ml = 8.93 g/ml.
Therefore, the density of the sample is 8.93 g/ml, which corresponds to option a).