________: program covering losses in income from commodity price declining reference prices

The productivity standard says

A) that everyone should have exactly the same income. B) that the age-earnings cycle should determine income. C) that people should be compensated on the basis of what they produce. D) that people should be compensated on the basis of their need.

Which of the schedules represent(s) a proportional tax?

Answer the question on the basis of the following five schedules, all of which represent income tax schedules for an economy. All figures are in billions of dollars.

A.  II and IV.
B.  III and V.
C.  IV only.
D.  I only.