1. The liver plays a vital role in digestion. What is one of the main functions of the liver in the digestive system?

A. Physical breakdown of food
B. Production of digestive enzymes
C. Storage and processing of nutrients
D. Elimination of waste products

Correct answer: C

Rationale: The correct answer is C: 'Storage and processing of nutrients.' The liver is a crucial organ in the digestive system as it performs various functions such as storing nutrients like glucose, vitamins, and minerals, processing nutrients by converting them into usable forms for the body, and regulating their distribution to different parts of the body. While the physical breakdown of food primarily occurs in the mouth and stomach, and the production of digestive enzymes mainly happens in the pancreas and small intestine, the liver's main role is to manage and store the nutrients obtained from the digested food. Therefore, option C is the correct choice for the main function of the liver in the digestive process.

2. What is the difference between DNA and RNA?

A. Both are double-stranded.
B. DNA contains deoxyribose sugar, while RNA contains ribose sugar.
C. RNA contains the nitrogenous base uracil, while DNA contains thymine.
D. Both are identical molecules.

Correct answer: B

Rationale: Rationale: A) Incorrect. DNA is double-stranded, but RNA is typically single-stranded. B) Correct. DNA contains deoxyribose sugar, which lacks an oxygen atom on the 2' carbon of the sugar ring, while RNA contains ribose sugar, which has an additional hydroxyl group on the 2' carbon. C) Incorrect. RNA contains the nitrogenous base uracil, while DNA contains thymine. D) Incorrect. DNA and RNA have distinct structures and functions, so they are not identical molecules.

3. Which of the following numbers is a perfect square?

A. 10
B. 12
C. 15
D. 16

Correct answer: D

Rationale: A perfect square is a number obtained by squaring an integer. 16 is the result of squaring 4 (4 x 4 = 16). The other answer choices are not the product of squaring any whole number.

4. The WBC (white blood cell) type responsible for the initial attack on pathogens is:

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

Correct answer: C

Rationale: The correct answer is C: Phagocytes. Phagocytes are a type of white blood cell that plays a crucial role in the immune response by engulfing and destroying pathogens. They are the first line of defense against invading microorganisms, initiating the initial attack on pathogens. Red blood cells (option A) are responsible for carrying oxygen, not for immune responses. Platelets (option B) are involved in blood clotting. Lymphocytes (option D) are another type of white blood cell but are mainly responsible for specific immune responses rather than the initial attack on pathogens.

5. Myelin sheath is a fatty substance that insulates and protects the long extensions of some nerve cells. It is produced by:

A. Schwann cells
B. Astrocytes
C. Neurons
D. Oligodendrocytes

Correct answer: A

Rationale: The correct answer is A: Schwann cells. Schwann cells are a type of glial cell in the peripheral nervous system that produce the myelin sheath around axons. Myelin sheath is essential for the rapid conduction of nerve impulses and provides insulation and protection to nerve fibers. Astrocytes are glial cells that provide support and maintain homeostasis in the central nervous system, but they do not produce myelin. Neurons are the main functional units of the nervous system responsible for transmitting nerve impulses. Oligodendrocytes are another type of glial cell in the central nervous system that produce myelin sheath around axons in that region, not in the peripheral nervous system where Schwann cells are responsible for myelination.

6. Differentiate between epithelial and connective tissue.

A. Epithelial tissue is exclusively found in the lungs, while connective tissue supports tendons.
B. Both are composed of cells, but epithelial tissue lines surfaces and glands, while connective tissue binds other tissues.
C. Epithelial tissue is more vascularized, while connective tissue is responsible for muscle contraction.
D. Epithelial tissue is the largest tissue type, while connective tissue is the smallest.

Correct answer: B

Rationale: Epithelial tissue covers surfaces and lines organs, while connective tissue provides support and structure throughout the body. Both are composed of cells, but their functions and locations differ.