Sentence:  (A) <WSD>conspiracy theory</WSD> is simply a theory that posits a conspiracy – a secret plan on the part of some group to influence events by partly secret means. 
Meaning of the word marked with <WSD> tags:  A hypothesis alleging that the members of a coordinated group are, and/or were, secretly working together to commit illegal or wrongful actions including attempting to hide the existence of the group and its activities. In notable cases the hypothesis contradicts the mainstream explanation for historical or current events. (1960s)