"... hence the maximum likelihood estimator is said to be asymptotically
efficient because its variance equals this lower bound". In this case they are
referring to the Rao-Cramer lower bound.
Option 2 from #20 on the exam reads "The variance of the estimator is equal to
the Rao-Cramer lower bound." According to the above, this statement is true.
Since H&K never mention any conditions on this (i.e. small samples), I'd have
to say that "C" is the correct answer.