Which of the following is not one of Wallas' four stages of scientific problem solving?

Which of the following is not one of Wallas' four stages of scientific problem solving?
 
  a. illumination
  b. induction
  c. incubation
  d. verification

Question 2

You've recently become interested in dreaming and have read many articles about it. In which of the following stages are you most likely to be in?
 
  a. illumination
  b. induction
  c. incubation
  d. preparation

Question 3

Wallas found that one of the things that scientists do to solve problems is to learn all they can about a problem and to examine it from varied perspectives. This stage of scientific problem-solving is called:
 
  a. preparation.
  b. incubation.
  c. illumination.
  d. verification.