Consider the sequence $(u_n)$ defined for every natural number $n$ by:
$$u_n = \mathrm{e}^{2n+1}$$
The sequence $(u_n)$ is:\\
a. arithmetic with common difference 2;\\
b. geometric with common ratio e;\\
c. geometric with common ratio $\mathrm{e}^2$;\\
d. convergent to e.