A scientist had been working in the canyon. 

A. One day a scientist found a long, thin piece of silk at the bottom of the canyon, yet he had been working in the canyon. 

B. One day a scientist found a long,thin piece of silk at the bottom of the canyon and he had been working there. 

C. One day a scientist who had been working in the canyon found a long,thin piece of silk at the bottom of the canyon.

D. No one was ever able to overtake the fleeing phantom ; because it always seemed to disappear into thin air.