The phrase about car alarms seems kind of random and disconnected from the rest of the argument, so it's purpose in the argument is going to be a bit different. This question is perhaps best explained by ruling out the wrong answers.
(A) says it justifies, which would imply it is a premise, but how does it further the argument? It doesn't function as a premise in the argument, so this is wrong.
(B) says it provides background information, but what background information does it provide? It doesn't add any background information, so this is wrong.
(D) how could this be the reason why police respond to burglar alarms over car alarms? Couldn't it be possible that burglar alarms are more effective because police respond to them? This also doesn't factor into the argument and is wrong.
(E) how would the statement in question explain why most false alarms are from businesses? This doesn't make sense either.
(C) says that it anticipates a potential objection - "you wouldn't fine someone every time a their car alarm goes off, why would you fine people with burglar alarms?" Allowing the conclusion to be made. This is the only explanation as to why this particular phrase would be included in the argument.
