Bottles containing $\mathrm{C}_6 \mathrm{H}_5$ l and $\mathrm{C}_6 \mathrm{H}_5 \mathrm{CH}_2 \mathrm{I}$ lost their original labels. They were labelled $\mathrm{A}$ and $\mathrm{B}$ for testing $\mathrm{A}$ and $\mathrm{B}$ were separately taken in test tubes and boiled with $\mathrm{NaOH}$ solution. The end solution in each tube was made acidic with dilute $\mathrm{HNO}_3$ and then some $\mathrm{AgNO}_3$ solution was added. Substance B gave a yellow precipitate. Which one of the following statements is true for this experiment?