A progressive tax system: a) Means higher marginal tax rates at higher income levels.
b) Provides more work incentives than a system with constant marginal tax rates.
c) Promotes more investment than a system with constant marginal tax rates.
d) All of the above.

a) Means higher marginal tax rates at higher income levels.

Explanation:

The progressive tax system is a system where the rate of the taxes according to the increased in the taxable amount. It generally applied to the personal income taxes that means if the people have the less income so less tax rate would be applied and if the people have the high income so high tax rate is applied

Therefore as per the given situation, the option a is correct

answer; i believe the correct answer is (treasury bills);

answer; the above statement is (true);