The correct answer is B). Description.
MacGregor mainly engages the reader through the use of a DESCRIPTION.
The author is describing to detail the chronometer and what it produces in the 19th century. This description engages the reader to be more interested in the topic. The description goes on with the example of the Great Western Railway of 1840 and the application of standard time.
A description is a statement where someone gives the characteristics of something or a person, detailing aspects of the individual or the situation.