Final answer:
Recall bias and misclassification are biases most readily avoidable in a prospective cohort study when measuring exposure, as data are collected prospectively, reducing the influence of participants' memories, and validated measures can be used.
Step-by-step explanation:
In measuring an exposure in a prospective cohort study design, the biases that are most readily avoidable include recall bias and misclassification. Recall bias is reduced in a prospective design since data on exposures are collected before the development of outcomes. Thus, participants' memories of past exposures do not influence the study. Misclassification can also be minimized by obtaining exposure information prospectively and by using validated measures. Confounding, healthy worker effect, and the Hawthorne effect are biases that relate to study conditions and participant behaviors rather than memory and classification issues.
Confounding is a mixing of effects that happens when the relationship you are interested in is mixed with the effect of something else. The Hawthorne effect refers to a situation where subjects modify an aspect of their behavior in response to knowing that they are being studied. While these effects are important to consider, they are not the most readily avoidable in the context of a prospective cohort study when focusing on the measurement of exposure.