What is essential to start the process of thinking?

Correct option is D

Thinking is the ability to engage in the process of problem-solving, planning and organizing, finding information, critical thinking, significant use of memory and decision making.
 According to Ross, “Thinking is a mental activity in its cognitive aspect or mental ability with regard to psychological object.”
 According to Garrett, “Thinking is behavior which is often implicit and hidden and in which symbols (images, ideas and concepts) are ordinarily employed.”
 Thinking refers to an individual’s ability to make decisions and solve problems.
 When beginning to think one must necessarily begin with something. This something, offering itself to and intellectual concern, need, problems, etc.
 Thinking process starts with the question (problem) and then move towards the solution.