The answer is
A. Hand washing
Answer: The gateway drug effect (alternatively, stepping-stone theory, escalation hypothesis, or progression hypothesis) is a comprehensive catchphrase for the often observed effect that the use of a psychoactive substance is coupled to an increased probability of the use of further substances.
Explanation:
The correct answer is the left atrium receives the newly oxygenated blood.
The ends of the femur are covered in a smooth, slippery substance called articular cartilage. This cartilage protects and cushions the bone when you bend and straighten your knee. The normal anatomy of the knee.