When a sequence $\left\{ a _ { n } \right\}$ satisfies $n < a _ { n } < n + 1$ for all natural numbers $n$, what is the value of $\lim _ { n \rightarrow \infty } \frac { n ^ { 2 } } { a _ { 1 } + a _ { 2 } + \cdots + a _ { n } }$? [3 points]\\
(1) 1\\
(2) 2\\
(3) 3\\
(4) 4\\
(5) 5