Final answer:
The student is experiencing vacillation due to this double approach-avoidance conflict. So, the correct answer is option c.
Step-by-step explanation:
The student is experiencing vacillation due to this double approach-avoidance conflict. Vacillation refers to being indecisive or uncertain, which is evident in the student's switching between studying for one test and then thinking about the need to study for the other. The conflict is double approach-avoidance because the student wants to make a good grade on both tests but lacks the time to study adequately for both. So, the correct answer is option c.