The automobile has tended to destroy without any trace the difference between rural and urban life.

The correct answer is C. Obliterate.

The other options are:

• A. Cancel: to make something no longer exist or be effective.
• B. Negate: to make something untrue or invalid.
• D. Nullify: to make something ineffective or invalid.

The automobile has had a profound impact on the way we live, work, and travel. It has made it possible for people to live in rural areas and commute to jobs in urban areas, and it has also made it possible for people to travel long distances quickly and easily. This has led to a blurring of the distinction between rural and urban life.

The word “obliterate” means to destroy something completely, so it is the best choice for this question. The other options do not accurately reflect the impact of the automobile on rural and urban life.