A college professor hypothesizes that readers will comprehend more when reading a graphic novel than when reading text with no illustrations. To conduct an experiment, the professor will assign some students to the control group with a reading assignment in paragraph form and other students to the treatment group with a reading assignment in graphic novel form. Afterwards, all the students will take a quiz about the reading to measure comprehension. To assign the groups, the professor will split the students into five groups according to their current grade in the class: A, B, C, D, or F. Within each group, half of the students will be assigned to the treatment group with the graphic novel, and the rest will be assigned to the control group with the paragraph.

The characteristics of the treatment and control groups

should be roughly equivalent because the students are from a randomly chosen class.
might not be roughly equivalent because the students could have vastly different views about graphic novels.
should be roughly equivalent because both groups have a mixture of students with different current grades.
might not be roughly equivalent because the students were not labeled and randomly chosen for each group.