I'm trying to do a case-sensitive search in Nano. The help menu at the bottom of the screen says I can toggle case-sensitivity by typing `M-C`.

```
^G Get Help         ^Y First Line       ^T Go To Line       ^W Beg of Par       M-J FullJstify      M-B Backwards
^C Cancel           ^V Last Line        ^R Replace          ^O End of Par       M-C Case Sens       M-R Regexp

```

I'm not sure how to do this. Does `M-` refer to a modifier key that should be held while I type `C`? Or does `M-` mean I should press some key or key combination before hitting `C`?