The correct answer is option B.
n object with a volume of 3.91 × 10-24 nm3 and a mass of 7.93 × 10-1 ng is the most dense.
Density is the mass per unit volume. In all the options mass and volume are given but in different units, first convert volume into L, cm3 or ml and mass to g or kg and then we can calculate the density by using the formula:
Density = Mass / Volume