We have summary data on $20-$year returns on $4$ different types of investments:

Investment type Average Return Standard Deviation

A $19\mathrm{.}214\mathrm{.}1$

B $15\mathrm{.}614\mathrm{.}0$

C $11\mathrm{.}516\mathrm{.}8$

D $6\mathrm{.}71\mathrm{.}9$

Based on the above information rank order the investments in terms of highest to lowest

variability. As an example, if we were to rank the investments on the basis of their average, we

would rank them A$-$B$-$C$-$D