In the following passage, some of the words have been left out. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.
One should always keep in mind that psychology is essentially a laboratory science, and _________ a text-book subject. The laboratory material is to be_________ in ourselves. While the text should be thoroughly mastered, its statements should always be verified__________ reference to one's own experience, and observation of others. Prospective teachers should constantly correlate the lessons of the book ________the observation of children at work in the school. The problems suggested for__________ and introspection will, if mastered, do much to render practical help to find the truths of psychology.
suggested for _____________ and introspection will

Options

A. observe
B. observes
C. observed
D. observation

Answer

D