AMC 12A 2002 Problem 3

According to the standard convention for exponentiation,$$
2^{2^{2^{2}}}=2^{\left(2^{\left(2^{2}\right)}\right)}=2^{16}=65,536 .

If the order in which the exponentiations are performed is changed, how many other values are possible? **Answer Choices** A. $0$ B. $1$ C. $2$ D. $3$ E. $4$