Which of the following is phenolic?

Which of the following is the weakest acid?

Which reagent is used in the conversion of phenol to picric acid?

What product is obtained during the hydrogenation of phenol in the presence of a nickel catalyst at $160\,^oC$?

Picric acid is (at $25\,^{\circ}C$)

Benzene $+ HNO_{3(conc.)}$ $\xrightarrow{H_2SO_4} A$ $\xrightarrow[{(ii) OH^{-}}]{{(i) Sn/HCl}} B$ $\xrightarrow[{0 - 5 \ ^oC}]{NaNO_2 + HCl} C$ $\xrightarrow{H_2O/H^{+}} D$. What is $D$?