Objective means that they are "facts", and do not include personal thoughts and beliefs (which is subjective).
In this case, your answers are:
1) Fact:
Facts are made based on data and analysis, and are supported by details and other known "facts" or truths. This means that they are right in any circumstances in most cases, or at least in the given circumstance that is provided.
2) Data:
Data is used to support the fact, which is objective. Without data, the claim would be seen as a opinion, or subjective, in meaning, a "I feel that it is this way". Without data, you will not have facts.
It is not:
3) Opinion:
Opinion is the antonym of Fact, and so if Fact is a answer choice, then Opinion is not. Opinion is based off of feelings, personal knowledge, and personal preferences. While useful in some cases, it is not objective.
4) Theory:
A theory is not objective, because it is a opinion that is provable (but is yet to be proven). This makes it subjective, until proven right.
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