Most standardized tests, including college entrance exams, require students to fill in their answers on an answer sheet that requires the darkening of a circle. These bubbles, if you would, allow the test to be corrected simply and swiftly. These scantron sheets become a practice for younger students as they decide which answer they will choose using the McCall-Crabbs Comprehension Tests. They also provide a means of tracking the student's comprehension progress and become a vaulable part of their cumulative file.