Let $A$ be an $n \times n$ matrix with complex entries. Pick out the true statements.
- $A$ is always similar to an upper-triangular matrix.
- $A$ is always similar to a diagonal matrix.
- $A$ is similar to a block diagonal matrix, with each diagonal block of size strictly less than $n$, provided $A$ has at least $2$ distinct eigenvalues.
I have solved $1$ & $2$. $1$ is true and $2$ is false.
But I cannot find how to solve $3$. Can somebody help?