Which of the Three Following Groups,studied by Psychologist Charles Garfield,improved

Which of the three following groups,studied by psychologist Charles Garfield,improved the most in speechmaking abilities?

A) Group 1 read and studied how to give public speeches,but delivered no actual speeches.
B) Group 2 read about speechmaking and also gave two talks each week to small audiences of classmates and friends.
C) Group 3 read about effective speaking and gave one talk each week to small groups.This group also watched videotapes of effective speakers and,twice a day,mentally rehearsed giving effective speeches of their own.