The second choice is a fragment, not a complete sentence.
I believe the correct choice is number one, because if you turn the sentence around, it answers the question of why the crowd is gathered. You may want to confirm on the website chompchomp.com (Grammar Bites).
All of them but 'Person vs. Self'
It was a strange experience and it confused him which causes him to be angry at himself
Hi , well the second one is basically the one that makes sense , so your correct answer is B.
