Answer: a. A prerequisite must be taken before another course; a corequisite and another course must be taken together.
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Explanation:
A prerequisite to calculus is precalculus since you must take precalculus before calculus. The "pre" indicates "before".
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As for corequisite, you could have a biology course and a lab that goes with it. Though usually labs are considered part of the class. It will depend on how the course is structured.
Another example of corequisite classes could be taking a statistics course focused on psychology majors and also some other psychology course dealing with sampling techniques.
The "co" means "together".
