1. The primary function of the respiratory system is to:

A. Maintain body temperature
B. Deliver oxygen to the bloodstream and remove carbon dioxide
C. Produce antibodies for the immune system
D. Break down food molecules for energy

Correct answer: B

Rationale: The correct answer is B: 'Deliver oxygen to the bloodstream and remove carbon dioxide.' The primary function of the respiratory system is to facilitate gas exchange. When we breathe in, oxygen is inhaled and transported to the bloodstream, where it is delivered to cells for energy production. Simultaneously, carbon dioxide, a waste product of cellular metabolism, is removed from the bloodstream and exhaled. This process is vital for sustaining life and maintaining proper oxygen levels in the body. The respiratory system does not primarily regulate body temperature, produce antibodies, or break down food molecules for energy, making options A, C, and D incorrect.

2. What is the term for the shedding of the outermost layer of the epidermis?

A. Desquamation
B. Exfoliation
C. Keratinization
D. Epidermolysis

Correct answer: A

Rationale: The correct term for the shedding of the outermost layer of the epidermis is desquamation. Desquamation is a natural process where old skin cells are shed off to make way for new cells. Exfoliation refers to the removal of dead skin cells through external means like scrubs. Keratinization is the process by which skin cells produce the protein keratin, while epidermolysis is a condition where the epidermis separates from the dermis. Therefore, in this context, desquamation is the most appropriate term for the shedding of the outermost layer of the epidermis.

3. What is the main verb tense in the following sentence? "She had already left before I arrived."

A. Present tense
B. Past tense
C. Future tense
D. t perfect tense

Correct answer: D

Rationale: The verb "had left" is in the past perfect tense, indicating an action completed before another past action ("arrived").

4. What is the name of the white blood cells that attack foreign invaders?

A. Phagocytes
B. Lymphocytes
C. Platelets
D. Red blood cells

Correct answer: A

Rationale: Rationale: Phagocytes are a type of white blood cell that plays a crucial role in the immune system by engulfing and digesting foreign invaders such as bacteria, viruses, and other harmful substances. They are part of the body's innate immune response and are essential for protecting the body against infections. Lymphocytes, on the other hand, are another type of white blood cell involved in the adaptive immune response, producing antibodies and coordinating immune responses. Platelets are cell fragments involved in blood clotting, while red blood cells are responsible for carrying oxygen to tissues.

5. Which organ helps break down food by grinding it with your teeth?

A. Stomach
B. Esophagus
C. Liver
D. Mouth

Correct answer: D

Rationale: Rationale: The mouth is the organ that helps break down food by grinding it with your teeth. The process of chewing, also known as mastication, breaks down food into smaller pieces, making it easier to swallow and digest. The teeth in the mouth play a crucial role in this initial stage of digestion by physically breaking down food into smaller particles. The other options listed do not directly participate in the mechanical breakdown of food through chewing.