The authors of Chapter 1 ("Defining the Field of Applied Social Psychology") propose that

A) a central focus of the field of applied social psychology is on practical problems, as well as on social problems
B) problems such as smoking and HIV/AIDS are nonsocial at a basic biological level and thus are not especially amenable to social psychologically based solutions
C) understanding group dynamics among teams is the core focus of applied social psychology
D) social psychology has a more applied focus than applied social psychology

The authors assert that the central focus of applied social psychology is on practical problems, which may include both social and nonsocial issues. This aligns with the definition of applied social psychology as the application of social psychological theories and principles to practical problems. Choice B is incorrect because the authors do not suggest that issues like smoking and HIV/AIDS are not amenable to social psychological solutions. Choice C is incorrect because while understanding group dynamics is a part of applied social psychology, it is not the sole focus. Choice D is incorrect because social psychology is a more general field that may include both basic and applied research, while applied social psychology is specifically focused on the application of social psychological research to practical problems.