Gas Particles Travel at Speeds of Up to 500 Meters

Multiple Choice

Gas particles travel at speeds of up to 500 meters per second. Why, then, does it take so long for gas molecules to travel the length of a room?

A) It doesn't. The fact is that a high concentration of them is required in order for them to be detected.
B) Gas particles travel in circular motion expanding outward as the move.
C) Gas particles bump into each other as well as other particles in the air.
D) Strong attractive forces between the gas particles keep the individual particles from high speed escape.