A regressive tax is (when a tax) imposes a heavier burden on low-income taxpayers than on high-income tax payers.
a) same
c)a tax where it
d)one that
i know why (a) is wrong bc tax cannot impose but what are the differences between (c) and (d)… aren’t those both using ambiguous pronouns which are “one” and “it”?

How is “one” ambiguous? It clearly refers to tax.

In the sentence, “A bad dog is one that bites people,” clearly the “one” refers to “dog.”

The problem with C is also not ambiguous pronoun usage. It’s the “where.” That’s a word for places, not taxes. 🙂