Final answer:
The correct answer is 'a) Circumnavigate,' which is the term for sailing or flying around the Earth.
Step-by-step explanation:
The 14-letter word that means to sail or fly around, especially around the Earth is circumnavigate. Option a) Circumnavigate is the correct choice because it specifically describes the action of traveling all the way around the Earth by sea or air. Options b) Encircle and d) Surround can both mean to enclose or to go around something, but they do not necessarily imply a complete journey around the Earth. Option c) Orbit is typically used to refer to the path that objects in space (like satellites or planets) take around another body, rather than a journey taken by people.