What is the limit of $\sum _ { k = 1 } ^ { n } \frac { e ^ { - k / n } } { n }$ as $n$ tends to $\infty$ ? (A) The limit does not exist. (B) $\infty$ (C) $1 - e ^ { - 1 }$ (D) $e ^ { - 0.5 }$
What is the limit of $\sum _ { k = 1 } ^ { n } \frac { e ^ { - k / n } } { n }$ as $n$ tends to $\infty$ ?\\
(A) The limit does not exist.\\
(B) $\infty$\\
(C) $1 - e ^ { - 1 }$\\
(D) $e ^ { - 0.5 }$