Is______necessary to change trains at Beijing?

Many people complained about the stones lying on a road, but _______ did anything about getting the stones out of the way.

The waste from the paper factory has poisoned all the fish to death--- _____ is left.

Life in cities is much livelier than ________ in the country.      

Cook was a strict but good captain , _____ who , usually , took care of the sailors on his trip .