George Used the classical experimental Design to Test Ways to Raise

George used the classical experimental design to test ways to raise self-assurance in stressful situations. He gathered 100 students from Introduction to Psychology in a room and randomly assigned each to one of two groups. His independent variable was a toy called Rubik's Cube, in which a person needs to manipulate boxes bound together in a multi-colored cube to align their colors, and he created stress by having a large clock in the room. The dependent variable was speed in getting the Cube's colors to align. He measured the level of self-assurance of people in one group with a questionnaire with 15 Likert scale items; then had them manipulate Cubes that were rigged to be easy. They answered another self-assurance questionnaire after completing the task. He measured self-assurance in the second group with the same questionnaire; then had the people manipulate Cubes that were rigged to be impossible to solve. The subjects answered another self-assurance questionnaire after 50 minutes of trying to complete the impossible task. In what part of the experiment does George measure the level of his dependent variable after he introduced the independent variable?

A) control group
B) experimental group
C) pretest
D) posttest
E) random assignment