1. Fingernails and toenails are made primarily of:

A. Collagen (Collagen is found in the dermis)
B. Keratin
C. Melanin (Melanin provides pigment, not structure)
D. Sebum (Sebum is an oily substance)

Correct answer: B

Rationale: The correct answer is B: Keratin. Fingernails and toenails are primarily made of a tough protein called keratin. Keratin is a fibrous structural protein that also makes up hair and the outer layer of skin. Collagen, as mentioned in option A, is found in the dermis of the skin and is responsible for providing strength and elasticity to the skin. Melanin, as in option C, is a pigment that gives color to the skin, hair, and eyes, but it does not contribute to the structure of nails. Sebum, as in option D, is an oily substance produced by the sebaceous glands in the skin to moisturize and protect the skin, but it is not a component of nails.

2. When proofreading your writing, focus on:

A. Changing the wording to sound more original.
B. Ignoring minor grammatical errors like typos.
C. Checking for clarity, consistency, and overall flow.
D. Replacing common words with thesaurus alternatives.

Correct answer: C

Rationale: Proofreading involves correcting errors, refining sentence structure, and ensuring the writing achieves its purpose, clarity, and consistency.

3. The primary function of the placenta during pregnancy is to:

A. Produce insulin
B. Facilitate gas exchange between mother and fetus
C. Excrete waste products from the fetus
D. All of the above

Correct answer: D

Rationale: The correct answer is D, 'All of the above.' The placenta serves multiple crucial functions during pregnancy. It facilitates gas exchange between the mother and fetus, ensuring the transfer of oxygen and nutrients while removing carbon dioxide and waste products. Additionally, the placenta produces hormones like insulin that help regulate the mother's metabolism and support the development of the fetus. Therefore, the placenta plays a vital role in maintaining a healthy environment for the growing fetus by providing essential nutrients, removing waste, and regulating hormonal balance.

4. Which preposition best completes the sentence: "She borrowed money _____ her friend."

A. of
B. from
C. on
D. for

Correct answer: B

Rationale: "From" indicates the source of the borrowed money.

5. What happens to the frequency of a wave when its wavelength is doubled, assuming the speed remains constant?

A. Frequency remains the same.
B. Frequency is halved.
C. Frequency is doubled.
D. Frequency information is insufficient to determine.

Correct answer: C

Rationale: Since the wave speed is constant, if the wavelength increases, the frequency must decrease to maintain the same energy transfer per unit time.

6. Which element has the highest melting point of any element?

A. Tungsten
B. Iron
C. Platinum
D. Carbon

Correct answer: D

Rationale: Diamond's strong covalent bonds between carbon atoms make it incredibly resistant to heat and pressure, giving it the highest melting point.