In a Stylus Maze Study, Some Subjects Are Shocked for Errors

In a stylus maze study, some subjects are shocked for errors and others are not shocked. Also, some are told they'll earn $10 if they learn the maze in 5 trials and others are told they'll earn $100. The results are that whether or not shock was present had no effect on behavior, but those who could earn $100 learned faster than those earning just $10. This result is most clearly an example of

A) a main effect of shock
B) a main effect of incentive (money)
C) an interaction between shock and incentive
D) all of the above The next four questions refer to the following experiment:
A researcher studied the influence of crowding (low, medium, and high crowding) on reading comprehension between two types of third graders. Half the children randomly assigned to each crowding condition were classified as "good" and half "poor" on an assessment of verbal fluency. In the study, each child read a 750-word passage and was tested on it later.