Final answer:
Abstaining from sexual intercourse and oral sexual contact is the safest sexual behavior.
Step-by-step explanation:
The safest sexual behavior is option C, abstaining from sexual intercourse and oral sexual contact. Abstinence is the only method that completely eliminates the risk of sexually transmitted infections (STIs) and unintended pregnancy. While using condoms and contraceptive pills (option A) or relying on tubal sterilization or vasectomy (option B) can greatly reduce the risk of STIs and pregnancy, they are not 100% effective.