Duncker's Research on the Box Problem Showed That

Multiple Choice

Duncker's research on the box problem showed that

A) very few participants were able to solve the problem in any condition.
B) participants were less likely to solve the problem if the boxes contained other objects than it the boxes did not contain other objects.
C) participants were more likely to solve the problem if the boxes contained buttons than if the boxes contained candles.
D) the functional fixedness effect was not reliable.