The word "professional" in this advertisement most probably means “_______.”

A．Marianne Adam has had many photographs printed in magazines
B．Joseph Saimders has worked in New Urban ,University for over 12 years
C．Dr John Goode's method of stopping smoking is successful
D．many business education teachers have given successful lessons in typing before

A．on Saturdays and Sundays
B．from Monday to Friday
C．from Monday to Saturday
D．on each day in the week