Which letter is not homeomorphic to the letter $C$? Which letter is not homeomorphic to the letter $C$?
I think letter $O$ and $o$ are not homeomorphic to the letter $C$. Is that correct?
Is there any other letter?
 A: From the wikipage on topology, here are the equivalence classes (under homeomorphism) of letters of the English alphabet. Any letter not in the same bracketed set as 'C' is not homeomorphic to it.

A: There are many others $E$ or $Q$ for example. The most basic method I know of is by assuming there is one, then it restricts to the subspace if you take out one (or more) points. Then the number of connected components of this subspace is an invariant.
A: That's right. Also, $B$ is not homeomorphic to $C$ since homeomorphic letters have same fundamental groups but $\pi_1(C) = 0$ and $\pi_1(B) = \mathbb Z \ast \mathbb Z$.
Alternatively, you could argue that if you remove any point from $C$, except one of the two endpoints, then $C$ is no longer connected whereas if you remove one point from $B$, no matter which point you remove, $B$ will still be a connected space. 
A: O is not homeomorphic to C: they're not even homotopic since O has one hole and C has zero. B has two holes and is homeomorphic to neither C nor O.
