Read the following passage and answer the questions that follow .
Vehicles do not move about the roads for mysterious reasons of their own. They move only because people want them to move in connection with the activities which the people are engaged in. Traffic is therefore a ‘function of activities’, and because, in towns, activities mainly take place in buildings, traffic in towns is a ‘function of buildings’. The implications of this line of reasoning are inescapable.
By ‘this line of reasoning’, the author means

Options

A. idea contained in this line.
B. idea contained in any one line of his argument.
C. the manner of arguing.
D. this row of printed characters.