You purchase a $30-$year, zero$-$coupon bond for a price of $$40.$ The bond will pay back $$100$ after $30$ years and make no interim payments. The annual compounded retum $($geometric average return$)$ on this investment is:

A$.3\mathrm{.}1\%$

B$.2\mathrm{.}64\%$

C$.2\mathrm{.}95\%$

D$.3\mathrm{.}72\%$