23) Which of the following expressions represents half of $4^{1998}$?
(A) $2^{1998}$
(B) $4^{1997}$
(C) $2^{999}$
(D) $4^{999}$
(E) $2^{3995}$
23) The answer is (E).

Indeed, we have $\frac{4^{1998}}{2}=2^{1998 \cdot 2-1}=2^{3995}$.