73 The sequence $\left\{\frac{100^{n}}{n!}\right\}(n=1,2,3, \cdots)$ is
A. an increasing sequence
B. a decreasing sequence
C. a sequence that has both increasing and decreasing terms after the 1993rd term
D. a sequence for which there exists a term such that after this term, it is decreasing
$73 \mathrm{D}$.
$$
\frac{a_{n+1}}{a_{n}}=\frac{\frac{100^{n+1}}{(n+1)!}}{\frac{100^{n}}{n!}}=\frac{100}{n+1} .
$$

It is easy to see that when $n>99$, the value of (1) is less than 1, meaning $\{a\}$ is decreasing.