Describe the location and importance of cilia and mucus in the respiratory system.

Tiny hairs called  cilia  protect the nasal passageways and other parts of the  respiratory  tract, filtering out dust and other particles that enter the nose with the breathed air.

I’m going to guess these are the choices: a) recreational skiing developed in the mid-19th century b) it was originally invented as a way of getting from place to place in snowy regions c) downhill skiing is currently the only common form of the sport d) it mostly evolved from snowshoeing- if that’s the cases then the answer would be c) downhill skiing is currently the only common form of the sport