Why Do Small Changes in Productivity Growth Rates Have Large

Multiple Choice

Why do small changes in productivity growth rates have large long-term effects on economic growth over the long run?  

A)  because lower productivity growth makes labour discouraged, which compounds the problem 
B)  because the effects of lower productivity growth on the economy are compounded over the years, which leads to large cumulative effects 
C)  because when the productivity growth rate falls, output actually falls 
D)  because lower productivity growth for one resource means lower productivity growth for all resources