Find the Following Limit, If It Exists $\lim _ { x \rightarrow 3 } x ^ { 7 }$

Find the following limit, if it exists. $\lim _ { x \rightarrow 3 } x ^ { 7 }$

A) 3
B) 21
C) $- 3$
D) 2187
E) The limit does not exist.