1. Melanin, the pigment responsible for skin color, is produced by

A. Keratinocytes (These cells produce keratin)
B. Melanocytes
C. Sebocytes (These cells produce sebum)
D. Langerhans cells (These cells are part of the immune system)

Correct answer: B

Rationale: The correct answer is B: Melanocytes. Melanin, the pigment responsible for skin color, is produced by melanocytes, which are specialized cells located in the skin's epidermis. Melanocytes transfer melanin to keratinocytes, the predominant cell type in the epidermis, where it provides protection against UV radiation. Sebocytes produce sebum, an oily substance that helps moisturize the skin and hair. Langerhans cells are a type of immune cell that play a role in the skin's immune response. Therefore, the correct answer is B as melanocytes are specifically responsible for producing melanin.

2. Which hormone, produced by the pituitary gland, stimulates the production of milk in mammary glands during breastfeeding?

A. Growth hormone (GH)
B. Thyroid-stimulating hormone (TSH)
C. Prolactin
D. Follicle-stimulating hormone (FSH)

Correct answer: c

Rationale: The correct answer is C: Prolactin. Prolactin is the hormone produced by the pituitary gland that stimulates the production of milk in the mammary glands during breastfeeding. It plays a crucial role in lactation by promoting the growth and development of the mammary glands and initiating the production of milk. Growth hormone (GH) regulates growth and metabolism, not milk production. Thyroid-stimulating hormone (TSH) stimulates the thyroid gland, not mammary glands. Follicle-stimulating hormone (FSH) is involved in reproductive processes, not milk production. Therefore, prolactin is the hormone directly responsible for stimulating milk production during breastfeeding.

3. What is the main function of the large intestine?

A. Break down food
B. Absorb water
C. Secrete digestive enzymes
D. Store waste

Correct answer: B

Rationale: The correct answer is B: "Absorb water." The main function of the large intestine is to absorb water and electrolytes from the undigested food material that passes through it. This helps in the formation of solid waste or feces, which is then stored in the rectum until it is eliminated from the body. Breaking down food primarily occurs in the small intestine, while the large intestine focuses on reabsorbing water to prevent dehydration. Secreting digestive enzymes is mainly done by the pancreas and liver, not the large intestine.

4. What is the least common multiple (LCM) of 4 and 6?

A. 24
B. 12
C. 6
D. 3

Correct answer: B

Rationale: The LCM is the smallest number that is a multiple of both 4 and 6. We can find this by listing out the multiples of each number until we find a common value. In this case, 12 is the first number divisible by both 4 (4 x 3) and 6 (6 x 2).

5. Which of the following is an example of a nonpolar solvent?

A. Water
B. Ethanol
C. Acetone
D. Hydrochloric acid

Correct answer: B

Rationale: Rationale: - Water (option A) is a polar solvent due to its uneven distribution of charge, with the oxygen atom being partially negative and the hydrogen atoms being partially positive. - Ethanol (option B) is a nonpolar solvent because it has a symmetrical molecular structure that does not result in significant charge separation. - Acetone (option C) is a polar solvent as it contains a carbonyl group that results in a partial negative charge on the oxygen atom. - Hydrochloric acid (option D) is a polar solvent due to the presence of the highly electronegative chlorine atom, which results in a partial negative charge.