Consider the formula d = , where
d represents density,
• m represents mass and has units of kilograms (kg), and
V represents volume and has units of cubic meters (mº).
Select an appropriate measurement unit for density.

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.