Many kinds of " thank you"

 There are various kinds of "thank you" in a day. I say "thank you" to a bus driver every morning. Next, I say it to a person who opens a door of our laboratory and who keeps the door open. When many problems occur during performing experiments, I say it many times, when I want to use your restriction enzyme, when I want to know where E. coli stocks are. When I eat lunch, I say it to a clerk of the cafeteria in my laboratory, who is very cheerful every day.
 I used to use a only kind of "thank you" in every situation when I didn't get used to this country. However, now I say various kinds of "thank you" according to the situations, sometimes quickly and sometimes cheerfully.