All but Which One of the Following General Statements About

All but which one of the following general statements about strikes is true?

A) The pattern by industry,jurisdiction,and public vs.private- sector status has been changing.
B) They are the major source of lost working time in the Canadian economy.
C) They may have positive effects.
D) Their frequency tends to be greatest at high points in the business cycle.
E) Different types of strikes tend to have different causes.