Final answer:
A fact is a statement that is proven to be true through experiments or observations, and it is the correct answer to the question of which statement is assured to be true in every aspect.
Step-by-step explanation:
The question is asking which kind of statement can be considered completely true in every aspect. The options are a fact, an opinion, a hypothesis, and a theory. Among these, a fact is a statement that is proven to be true and is established by experiment or observation under specific conditions. An opinion is a personal belief or judgment that is not necessarily based on fact or knowledge. A hypothesis is a tentative statement about reality that has yet to be tested. A theory is a well-substantiated explanation of some aspect of the natural world that is supported by a body of evidence but is not as absolutely certain as a law.