Abstract thinking and scientific reasoning generally do not begin to develop until:

A. middle adulthood.

B. young adulthood.

C. adolescence.

D. middle childhood.

My answer is D.

Depends on how you define young, middle. Abstract reasoning seldom occurs before age 7, and even then, just in a few. My own experience is that one sees the change between 8th grade and 10th grade, and by the 11th grade teaching physics is possible. Piaget developed his ideas on this,http://psychology.about.com/od/piagetstheory/p/formaloperation.htm and it centers on a period between age twelve to adulthood when people develop the ability to think about abstract concepts. Skills such as logical thought, deductive reasoning and systematic planning also emerge during this stage. But I stick to my observations of students between 8th and 10th grade. So I guess I would go with answer C.