7. The value of \( \int_{0}^{2} f(x) d x \), where
\[
f(x)=\left\{\begin{array}{lc}
0, & \text { when } \quad x=\frac{n}{n+1}, n=1,2,3, \ldots . .10 \\
1, & \text { otherwise }
\end{array}\right.
\]
is equal to
(1) 10
(2) 2
(3) 30
(4) 0
[Limit of a Sum]
