According to federal regulations, "children" are defined as: Persons who have not yet attained the legal age of consent under the applicable laws in the jurisdiction in which the research was approved. Persons who have not yet attained the legal age of consent under the applicable laws in the jurisdiction in which the research will be conducted. Persons who are under 21 years of age. Persons who are under 18 years of age.

Persons who are under 18 years of age.

Explanation:

In the US, adulthood is gradually released to young people. Thus, with each age, some freedom is given to the young person who learns to create a sense of responsibility and is given the duties of adult citizen by parties. For them this is the best way to prepare youth for adulthood. However, it is legally accepted that at 18 years of age the young person is held responsible for his actions and is civilly and criminally responsible for them and is no longer considered a "child". Therefore, we can conclude that in the case of the research reported in the question above, persons who have not yet reached the legal age of majority in accordance with the applicable laws in the jurisdiction in which the research will be conducted are persons under 18 years of age.