This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
The fourth dimension of habit as described by Pinkham: 
Select and explain. 
A. Direction, B. Frequency, C. Intensity, D. Duration
A: Direction
Answer: A: Direction 
Explanation: Triad of a Habit
The deleterious effects produced by a habit depends upon the three factors – Duration, Frequency & Intensity.
 a. Duration: The amount of time spent indulging in the habit. 
 b. Frequency: The number of times the habit is activated in a day.
 c. Intensity: The vigor with which the habit is performed.
Key Concept:
Pinkham has added a fourth dimension to oral habits, ie., Direction.