Why can we never prove that a hypothesis is true?

Yes or no? if you are a bibliophile you probably like to read.

Cameron, who has an extreme and unreasonable suspicion of other people and their motives, suffers from paranoia which is a psychological disorder characterized by delusions of persecution or grandeur, was absolutely sure that someone was following him even though he was absolutely alone and hadn't seen a car for miles and miles.

Which statement contains an opinion? the ants serve to protect the acacia from other plants and herbivores. the acacia depends on pollinators for the exchange of genetic material. the acacia has no chemical defenses to discourage herbivores. the ants provide the acacia with the best protection from other plants and herbivores.