What Challenge Did Sociologist William Gamson Uncover in Attempting to Measure

What challenge did sociologist William Gamson uncover in attempting to measure the success of social movement groups?

A) Groups do not always fall into one category of success.
B) Most groups collapse before their success can be measured.
C) Not all groups report their activities so they can be studied.
D) Groups often have goals that are too small or too specific.