Final answer:
The correct answer is option b. Mr. Collins incorrectly believes Elizabeth's refusal to marry him is a test of his determination, failing to realize her disinterest is genuine.
Step-by-step explanation:
Mr. Collins refuses to accept that Elizabeth does not want to marry him primarily because he believes it's a test of his determination. This is a classic trope where the suitor is unable to interpret the refusal as sincere, convinced instead that the pursuit is just part of the courtship ritual and that a show of persistent determination will eventually be rewarded.
Despite Elizabeth's clear expressions of disinterest, Mr. Collins's mistaken belief in this social convention blinds him to the reality of her feelings, leading him to misinterpret her rejection as a mere challenge to be overcome.