Which of the following is a bond line structure of glycerol?

Which of the following has highest reactivity for $\mathrm{S}_{\mathrm{N}} 1$ reactions?

The reaction of bromobenzene with bromomethane and sodium metal in dry ether to give toluene is

What is the number of structural isomers possible for alkene with molecular formula $\mathrm{C}_5 \mathrm{H}_{10}$ ?