What is the example given by Kant to illustrate his notion of categorical imperative? I - The example of keeping a promise. II - The example of te...

What is the example given by Kant to illustrate his notion of categorical imperative?

I - The example of keeping a promise.
II - The example of telling a lie.
III - The example of being in a low mood most of the time.
IV - The example of lacking pleasure in some activity.
a) I and II are correct.
b) II and III are correct.
c) I and IV are correct.
d) II and IV are correct.