The solution to the problem involves analyzing both statements and determining their accuracy based on biological concepts:
Statement I: The presence or absence of hymen is not a reliable indicator of virginity.
This statement is true. The hymen, a thin membrane partially covering the vaginal opening, can be stretched or torn due to various non-sexual activities such as physical exercise, use of tampons, or even naturally. Therefore, its presence or absence does not reliably indicate sexual activity or "virginity."
Statement II: The hymen is torn during the first coitus only.
This statement is false. While coitus (sexual intercourse) can indeed result in the hymen being stretched or torn, it is not the only cause. As mentioned earlier, activities like cycling, horseback riding, or medical examinations can also affect the hymen. Thus, the statement that the hymen is only torn during first coitus is incorrect.
In conclusion, the logical analysis of both statements leads to the following answer: Statement I is true but Statement II is false.