A child experiences a serious and rare illness at three months old. A researcher studies this child until adulthood to learn about the impact of the illness on his family. What method is the researcher using? Case study Ob Experiment Observation Od Questionnaire A researcher provides one classroom of college students a list of 20 words to study while classical music plays in the background. Another classroom of college students is provided a list of 20 words to study in silence. After 20 minutes, the researcher records how many words each student remembers. What method is the researcher using? a Case study b Oc Experiment Observation d Questionnaire