A person whose opinion is important enough to affect one's self-concept strongly is a .

significant others                                  

Explanation:

In psychology, the term "significant other" is referred to as someone who gives very great importance to a person's well-being or life. It is described as an individual or individuals that possess a strong influence on a person's self-concept. It defined a specific relationship between two different people who share a bond and do not possess a married relation but carry a joint responsibility for oneself and the other.

In reference to the question above, the given statement refers to the "significant others".

answer; i believe the answer is 80%, plz check first good luck;

answer; the federal reserve system;