Final answer:
The requirement of an absence of more than 24 consecutive hours to consider a period as lost time is false. Additionally, if a woman's basal body temperature is still low on day 12 of her menstrual cycle, it is not safe to have unprotected sexual intercourse if avoiding pregnancy is the goal.
Step-by-step explanation:
The statement that there must be an absence of more than 24 consecutive hours before any period can be considered lost time is false. The context of this statement is not clear, but in general, periods of lost time can be considered on a case-by-case basis, depending on the specific definitions and rules set by the relevant authorities or agreements.
Regarding the question on menstrual cycles and contraception, if a woman is checking her basal body temperature each morning and today is day 12 of her menstrual cycle with her basal body temperature still low, it is not safe for her to have unprotected sexual intercourse if she wishes to avoid pregnancy. The days leading up to and around ovulation, which can occur around day 14 in a typical cycle, are when a woman is most fertile. A basal body temperature that has not yet risen may indicate that ovulation has not occurred yet, but it is still within the window of fertility.