13. When 3-methyl-2-pentene is treated with mercuric acetate, $\mathrm{Hg(O_2CCH_3)_2}$, in a THF-$t$-butyl alcohol mixture and the resulting product is reacted with $\mathrm{NaBH_4}$ in basic solution, the principal product formed is which of these? (A) 3-methyl-3-pentanol (B) 3-$t$-butoxy-3-methylpentane (C) 3-methyl-2-pentanol (D) 2-$t$-butoxy-3-methylpentane (E) 1-$t$-butoxy-3-methylpentane