In the reaction of phenol with ${\mathrm{CHCl}}_3$ and aqueous $\mathrm{NaOH}$ at $70 °\mathrm{C}(343 \mathrm{K}{)}_{,}$ the electrophile attacking the ring is:

The reaction can be classified as _____.

For the preparation of $\mathrm{t}-$butyl methyl ether by Williamson method, the correct choice of the reagents are