Which of the following alkyl groups has the maximum $+I$ effect?

Which acid of each pair shown here would you expect to be stronger?
$(i)$ $CH_3CO_2H$ or $CH_2FCO_2H$
$(ii)$ $CH_2FCO_2H$ or $CH_2ClCO_2H$
$(iii)$ $CH_2FCH_2CH_2CO_2H$ or $CH_3CHFCH_2CO_2H$
$(iv)$ $F_3C-C_6H_4-COOH$ or $H_3C-C_6H_4-COOH$

Which one of the nitrogen atoms in $H_2N-NH-CO-NH_2$ (where the atoms are labeled $I, II, III$ as shown in the structure) is the most nucleophilic?

The decreasing order of acidity of the following terminal acetylenes is:

Find the compound that has the maximum enol content.

Which of the following has zero inductive effect?