The Chi-square statistic is
\[
\chi^2=\sum\frac{(O-E)^2}{E},
\]
where \(O\) is the observed frequency and \(E\) is the expected frequency.
If the observed frequencies exactly equal the expected frequencies,
\[
O=E.
\]
Hence,
\[
(O-E)^2=0
\]
for every class.
Therefore,
\[
\boxed{\chi^2=0.}
\]
Thus,
\[
\boxed{(C)}
\]