@currybutterchicken The four who missed at least one class may not all have received lower than a B-. The prompt does not say that everyone who missed a class received lower than a B-, it says that "each student" who received a grade lower than a B- missed a class. The number of students who got below a B- is never expressly stated, so "each student" could be as low as just one student. Thus, we can't say for certain that they scored lower than a B- because that was left ambiguous.