Step 1: Recall the symmetry of sea anemone.
Sea anemone belongs to phylum Cnidaria.
Although cnidarians are generally radially symmetrical, sea anemone exhibits
\[
\boxed{\text{Biradial symmetry}.}
\]
Step 2: Choose the correct option.
Therefore,
\[
\boxed{(C)}
\]
is the correct answer.