For a repeated-measures study, if the null hypothesis is true, then what value should be obtained for the sample mean?

Raul is writing his psychology term paper on "attention deficit disorder.". To find information about his topic, he goes to a specialized online database offered by the American Psychological Association. He searches for his topic by entering the key words with each record in this database consisting of an abstract plus notes about the author, title, and source. Raul is using the online database

known as __________. Fill in the blank(s) with correct word

Are largely uncontrollable and are accompanied by physiological changes

A) ?Conflicts B) ?Pressures C) ?Stressors D) ?Emotions