To know a claim a priori is to know it to be true on the basis of reliable testimony.

The philosophical term “a priory” was popularized by Immanuel Kant and it concerns epistemology, philosophy dealing with the theory of knowledge. A priory actually refers to something that can be deduced by reason alone, while the "a posteriori" is something that cannot be known by reason alone like empirical facts.  

answer: fact: italy has over 300 islands ranging from extremely small uninhabited islands to the huge island of sicily.

explanation:

opinion: italy has way to many islands