False dilemma is a type of fallacy which is used when a speaker wants to narrow down options by making one option seem like the best and absolute and no other choices are available.
I don't know the passage where your questions comes from, ut the use of false dilemma would probably say something like, "Dogs are the most important pets to have" which limits the other pets which a person can have.
With this in mind, this is fallacious and is not true at all. So I would advise you to read the text again, <em>carefully </em>and note where the writer used words which limits the choice of other pets other than dogs and that is probably your answer.
Please note that your question is incomplete so I gave you a general overview so that you could better understand the concept.