$5\mathrm{.}7$ Rank the indicated protons in decreasing order of acidity.

a$)$ Most acidic: $,$ I $>$ IV $>$ II $>$ III $,$ Least acidic

b$)$ Most acidic: $,$ II $>$ III $>$ I $>$ IV $,$ Least acidic

$c$

$d$

e$)$ Most acidic: $,$ III $>$ II $>$ I $>$ IV $,$ Least acidic