The point about the systemic nature of the tension is first raised in the last paragraph. So, this cannot be the purpose of the claim we’re being asked about.

(B) does not capture the purpose of the claim we’re being asked about. You may think that (B) is something supported by the claim. (It isn’t actually supported, which I’ll explain in a moment). But even if it were supported, in order to be correct, it has to capture why the author wanted to tell us that some people in an adversarial system must lose. Here, given the sentences before and after the claim we were asked about, the purpose must relate to defining substantive justice. The author does convey to us that someone will lose – but the purpose of telling us that is to explain what substantive justice does not require.

The second reason (B) is wrong is that it’s not actually supported by the line we’re asked about. Although the author does say that someone must lose in an adversarial system, that does not imply that someone will always view the outcome as unfair. In fact, even a party that loses might still view the outcome as fair and legitimate, despite their loss.

The line we’re asked about is part of a section that defines substantive justice. The purpose of the line is not related to the flaws of formalism.

(D) is the best fit for the purpose we anticipated – helping to define substantive justice. The line we were asked about emphasizes what substantive justice is not. It’s not required to produce outcomes where everyone wins. In showing what substantive justice does not require, the author helps us understand what substantive justice does require.

Nothing in the second paragraph hints at the author’s later conclusion that formalism and substantive justice cannot be reconciled. The purpose of the line we’re asked about is to define substantive justice.