Solution
= Solution
{c}
The <monotone convergence theorem> states that if measurable functions $f_n$ are nonnegative and $f_n\uparrow f$ pointwise, then $f$ is measurable and
$$
\boxed{\int f\,d\mu=\lim_{n\to\infty}\int f_n\,d\mu,}
$$
allowing either side to be infinite. The same conclusion holds under almost-everywhere <monotone convergence> after changing values on a null set. No assumption that the integrals stay bounded is required.