The whole thing is kind of an insane exercise.
Xelawho is of course right.
If you come into the function with fullname
set to (example only) "zamboni".
Then at the end of the function the result will be that fullname
will contain "zamboni<b>zamboni<b></b>".
The only way to do this incredibly stupid question is directly:
fullname = "<b>" + fullname + "</b>";
Whoever designed that course should be taken out and shot.