\[\boxed{\mathbf{2}.}\]
\[\textbf{а)}\ f(x) = 0;\ \ F(x) = C;\]
\[F^{'}(x) = C^{'} = 0;\]
\[F^{'}(x) = f(x) - значит,\ \]
\[F(x)\ первообразная\ для\ f(x).\]
\[\textbf{б)}\ f(x) = 1;\ \ F(x) = x;\]
\[F^{'}(x) = x^{'} = 1;\]
\[F^{'}(x) = f(x) - значит,\ \]
\[F(x)\ первообразная\ для\ f(x).\]
\[\textbf{в)}\ f(x) = C;F(x) = Cx;\]
\[F^{'}(x) = \left( \text{Cx} \right)^{'} = C;\]
\[F^{'}(x) = f(x) - значит,\ \]
\[F(x)\ первообразная\ для\ f(x).\]
\[\textbf{г)}\ f(x) = x;\ \ F(x) = \frac{x^{2}}{2};\]
\[F^{'}(x) = \left( \frac{1}{2}x^{2} \right)^{'} = \frac{1}{2} \cdot 2x = x;\]
\[F^{'}(x) = f(x) - значит,\ \]
\[F(x)\ первообразная\ для\ f(x).\]
\[\textbf{д)}\ f(x) = x^{2};\ \ F(x) = \frac{x^{3}}{3};\]
\[F^{'}(x) = \left( \frac{1}{3}x^{3} \right)^{'} = \frac{1}{3} \cdot 3x^{2} = x^{2};\]
\[F^{'}(x) = f(x) - значит,\ \]
\[F(x)\ первообразная\ для\ f(x).\]
\[\textbf{е)}\ f(x) = x^{n};\ \ F(x) = \frac{x^{n + 1}}{n + 1};\ \ \]
\[n \in N;\]
\[F^{'}(x) = \left( \frac{x^{n + 1}}{n + 1} \right)^{'} = \frac{(n + 1)x^{n}}{n + 1} =\]
\[= x^{n};\]
\[F^{'}(x) = f(x) - значит,\ \]
\[F(x)\ первообразная\ для\ f(x).\]