If a taxpayer is in the $24\%$ marginal tax bracket, this means

a$)$ some of the taxpayer's income is taxed at $24\%$ but some portions of her income are taxed at lower rates

b$)$ none of these choices are correct

C$)$ all of her taxable income above $$160,200$ is taxed at $24\%$

d$)$ all of her taxable income is taxed at the $24\%$ rate