On average, personality traits differ from one part of the United States to another

A close relative of LSD, d-lysergic acid amide, is found naturally in

A. morning glories and Hawaiian baby woodroses. B. peyote cactus. C. henbane. D. opium poppies.

When researchers study the same sample over a long period of time, as was done in a number of longitudinal studies that were launched in the 1920s and 1930s, their results may be limited by all of the following phenomena except

a. lack of measurement equivalence b. attrition of participants c. practice effects d. lack of continuity