Researchers conducted a study to determine the effects of stress on the immune system by measuring immune system chemicals. to accomplish this goal, they compared college students who were undergoing a stressful series of exams to a group of similar students relaxing during a time of no classes and no exams. results of this study . the relaxed group showed no change over the course of the studyb. the exam group tested lower for immune system chemicalsc. the exam group tested higher for immune system chemicalsd. the relaxed group tested lower for immune system chemicals

B. The exam group tested lower for immune system chemicals.

Explanation:

The stress can have a negative influence over the immune system of a person. Typically the stress hormone cortisteroid can be responsible for suppressing the functioning of the immune system for example this hormone can lower the number of lymphocytes hence, defense mechanism of the body will slow down.

According to the given study, the effect of stress on the immune system is to be analyzed by measuring the amount of immune system chemicals. Among the two groups of college students, the group which was undergoing with exams is expected to secrete lower amount of immune system chemicals due to increase in stress during exams will suppress the functioning of immune system resulting in low secretion. But relaxed group will remain unaffected.