The world population first began exploding around what year?

Attention-deficit/hyperactivity disorder is best described by which of the following statements?

a) it is a neurodevelopmental disorder b) it is a misdiagnosis of a normal, highly active child c) it is a result of lack of discipline d) it is a disorder caused by early vaccinations

What is the most commonly used method in social science research?

a. case study b. survey or questionnaire c. experiment d. correlational study