What is the different usages of their, there, and they're

“third, all reviewers have a bias – no matter how impartial they try to be, opinions on movies are just that: opinions. this isn’t necessarily a bad thing: if you read a review by a critic that you know prefers foreign films, you know how seriously you should take his scathing critique of ironman.” according to this passage, all reviewers a. prefer foreign films c. have bias b. hated the movie ironman d. refuse to watch popular films