Concept:
Area under a piecewise-defined curve is obtained by integrating each piece separately over its interval.
Step 1: Split the area into two parts.
\[
A
=
\int_0^1 x^2\,dx
+
\int_1^4 \sqrt{x}\,dx
\]
Step 2: Evaluate the first integral.
\[\begin{aligned}
\int_0^1 x^2\,dx
&=
\left[\frac{x^3}{3}\right]_0^1
\\
&=
\frac13
\end{aligned}\]
Step 3: Evaluate the second integral.
\[\begin{aligned}
\int_1^4 \sqrt{x}\,dx
&=
\int_1^4 x^{1/2}\,dx
\\
&=
\left[\frac{2}{3}x^{3/2}\right]_1^4
\\
&=
\frac23(8-1)
\\
&=
\frac{14}{3}
\end{aligned}\]
Step 4: Find the total area.
\[\begin{aligned}
A
&=
\frac13+\frac{14}{3}
\\
&=
\frac{15}{3}
\\
&=
5
\end{aligned}\]
\[\begin{aligned}
\boxed{5}
\end{aligned}\]
Hence, option \(\mathbf{(A)}\) is correct.