Final answer:
The relative risk that suggests an exposure reduces the risk of an outcome is option a, which is 0.7. So, the correct answer is option a.
Step-by-step explanation:
The student is asking about relative risk, which is a measure used in epidemiology and public health to determine the association between exposure to a certain factor and the risk of a particular outcome. In a relative risk calculation, a value less than 1 suggests that the exposure may be associated with a reduction in risk of the outcome.
A relative risk of 1.0 indicates no difference in risk, while a value greater than 1 suggests an increased risk. Therefore, the relative risk that would suggest an exposure reduces the risk of an outcome is a. 0.7.