Hi @austinsheehy, thanks for your question. Look at lines 28-31 ("The absence of limitations upon the legal power of monarchs meant that there was no law or commitment monarchs could make that they could not also unmake or disregard."). Combine that with the last lines in the passage (59-63) which discuss how now it is Parliament that is unfettered in this way.
Taken together, these pieces of the passage support answer choice (C).