A Family with an Income of $25,000 Pays Taxes of $3,000

A family with an income of $25,000 pays taxes of $3,000 per year and a family with an income of $50,000 pays taxes of $4,000 per year.The tax plan is:

A) regressive.
B) proportional for all income levels.
C) progressive.
D) based on the ability-to-pay principle.
E) proportional for income levels between $25,000 and $50,000.