I don't like driving long distances - I prefer to go __ air.

• A. by
• B. on
• C. in
• D. with

Answer: (A)

Choosing the correct preposition shows how we express the method of travel. When talking about how you travel, English uses by + the mode: by car, by train, by boat, by air. In this sentence, the idea is travel by air, i.e., go by airplane. That makes the phrase natural and clear.

On air is used for broadcasting, as in being heard live; in air isn’t a standard way to describe travel and sounds incorrect here; with air would imply some accompaniment or tool, not the method of travel. So the best fit is by air.