Instructions:
Choose the Best Reagent(s) for Carrying Out the Following $a.~~~~~ \mathrm{CrO}_{3}, \mathrm{H}_{2} \mathrm{SO}_{4}, \mathrm{H}_{2} \mathrm{O}$

Instructions:
Choose the best reagent(s) for carrying out the following conversions from the list provided below. Place the letter of the best choice in the blank. Reagents may be used more than once.
$a.~~~~~ \mathrm{CrO}_{3}, \mathrm{H}_{2} \mathrm{SO}_{4}, \mathrm{H}_{2} \mathrm{O}$
$b.~~~~~$ 1. $\mathrm{NaBH}_{4}$ , ethanol
$~~~~~~~~$ 2. $\mathrm{H}_{3} \mathrm{O}$
$c.~~~~~$ 1. $\mathrm{LiA1}_{4}$ , ether
$~~~~~~~~$ 2. $\mathrm{H}_{3} \mathrm{O}^{+}$
$d.~~~~~~$ periodinane Refer to instructions. _____