Answer:
D. The colors and styles of old and new automobiles​
Step-by-step explanation:
A summary is a concise overview of a subject matter. When writing a summary, it is expected that the text be as precise as possible. The main points should be highlighted. A summary of the history of automobiles should have the main points such as the names of key inventors, the date specifying when the first car was driven, and the effects of these inventions.
Including details of the colors and styles of old and new automobiles will make the summary to become too wordy and lengthy. The readers might then lose the main point being conveyed.