## List filenames matching a pattern Solution
The solution is `3.`

`1.` shows all files whose names contain zero or more characters (`*`) followed by the letter `t`, then zero or more characters (`*`) followed by `ane.pdb`. This gives `ethane.pdb  methane.pdb  octane.pdb  pentane.pdb`. 

`2.` shows all files whose names start with zero or more characters (`*`) followed by the letter `t`, then a single character (`?`), then `ne.` followed by zero or more characters (`*`). This will give us `octane.pdb` and `pentane.pdb` but doesn't match anything which ends in `thane.pdb`.

`3.` fixes the problems of option 2 by matching two characters (`??`) between `t` and `ne`. This is the solution.

`4.` only shows files starting with `ethane.`.