Answer: d. allowing at least four nights to study for any major exam
Explanation:
Experts suggest that one needs enough time before they go for a major exam in which they can study and be able to retain information which will avoid the panic that may be brought by amount of work that need to be studied in a short period of time if someone has waited until the last minutes before they study.
One needs time to break the material into pieces as they study in order to be able to grasp the information and digest it and that requires time and it will be difficult if they do it for a lot of information at once.