Elimination of bromine from 2-bromobutane results in the formation of-

Alkyl halides react with dialkyl copper reagents to give

The compound formed on heating chlorobenzene with chloral in the presence concentrated sulphuric acid is

Bottles containing C₆H₅l and C₆H₅CH₂I lost their original labels. They were labelled A and B for testing A and B were separately taken in test tubes and boiled with NaOH solution. The end solution in each tube was made acidic with dilute HNO₃ and then some AgNO₃ solution was added. Substance B gave a yellow precipitate. Which one of the following statements is true for this experiment?