Of the following, which is the best example of appropriate praise given to a child?

A"no wonder your mother always calls you 'mr. clean.' you're always willing to clean up after yourself."

B"thank you for your help today in cleaning up the classroom. you really did a great job."

C"what a good guy you are. i know i can always count on you to help me clean up."

D"you're always so helpful. thanks for helping me clean up the classroom today."