VOA慢速英语:'A Princess of Mars,' by Edgar Rice Burroughs, Part One

trail - n. a path through a forest, field, etc.

Apache - n. a member of a Native American people of the southwestern U.S.

flee - v. to run away from danger (Irregular past tense: fled)

gravity - n. the natural force that tends to cause physical things to move towards each other : the force that causes things to fall towards the Earth

Martian - n. an imaginary creature in books, movies, etc., that lives on or comes from the planet Mars