TOEFL Reading: ETS-TOEFL阅读机经 - ZR115R06ED5PHVO3L$

The study conducted by Norman Triplett described in paragraph 3 supported the hypothesis that A. coaction effects are stronger on the performance of children than they are on the performance of adults B. coaction effects are limited to situations in which the time taken for a task matters C. people perform better when they know that their performance is being measured by someone D. people perform better in the presence of others who are doing the same thing they are