In 2018 the US Federal Corporate tax rate decreased from 35% to 21%. Other taxes remained largely the same. According to trade off theory you would expect that

a. firms will increase their debt-to-equity ratio by borrowing more to finance new projects as it is now more profitable to do so.

b. firms will issue more long-term debt and less short-term debt, leaving their debt-to-equity ratio unchanged.

c.firms will reduce their debt-to-equity ratio because the tax benefits of debt financing are now lower.

d.firms will pay out more dividends as they must pay less in corporate taxes, increasing their debt-to-equity ratio.