In the Study Done by De Morree, Klein, & Macora

In the study done by de Morree, Klein, & Macora (2012) on evidence for effort in the brain, what was the finding?

A) All of the above
B) Brain activity was greater when heavier weights were lifted
C) Brain activity was positively correlated with reported perceived effort
D) The brain worked harder to lift the weight when the arm was tired than when the arm was fresh