Now the ones I'm not too sure on

[*]
What letter does a single dash ( - ) signify in morse code ?
I?
[*]
Which rock group released the live album 'Made in Japan'?
I'm sure I know this one, but I can't think who! (I have the feeling it begins with an "R" but I'm not certain).
[*]
In the USA, Route 66 runs between which two cities ?
St Louis and Oklahoma City?
[*]
If something is cooked 'au gratin' what must it contain ?
Cheese?