Well it depends on what you mean by change.
One, but the lightbulb has to WANT to change.
Literally dozens.
Sorry we closed 18 seconds ago and I've just cashed up."
Two. One to change it and one to put some chips with it.
Depending what you're charged with can really effect how easily you're getting across.
Depends
Daughter: Well the principal kept going on about the school spirit.
I answer back... You mean in bed
Would you like ketchup with your chips
Because they philos all the time!