Under a particular tax system, the govt. collects $20 billion in tax revenues when GDP is $200 billion and $25 billion when GDP is $500 billion. Thistax systemis

A.Proportional becausetax rate remains unchanged even when GDP increases

B.Regressive becausetax rate decreases with increase in GDP

C.Progressive becausetax rate increases with increase in GDP

D.Regressive becausetax rate increases with increase in GDP