1. Sunscreen protects the skin from harmful ultraviolet (UV) rays by

A. Reflecting UV rays away from the skin
B. Absorbing UV rays and converting them to heat
C. Blocking UV rays completely
D. Stimulating melanin production

Correct answer: B

Rationale: The correct answer is B: Absorbing UV rays and converting them to heat. Sunscreen contains ingredients that act as filters to absorb UV radiation before it reaches the skin. These filters then convert the UV rays into a less harmful form of energy, usually heat, which is then released from the body. This process helps prevent UV radiation from damaging the skin cells and causing sunburn or long-term skin damage. Reflecting UV rays away from the skin (A) and blocking UV rays completely (C) are not accurate functions of sunscreen. Additionally, stimulating melanin production (D) is not a direct way in which sunscreen protects the skin from UV rays.

2. What type of waves require a medium (solid, liquid, or gas) to propagate?

A. Transverse waves
B. Longitudinal waves
C. Electromagnetic waves
D. Surface waves

Correct answer: B

Rationale: Longitudinal waves require a medium (solid, liquid, or gas) to propagate because the particles in the medium move parallel to the direction of the wave. Transverse waves, on the other hand, do not require a medium and can propagate through a vacuum. Electromagnetic waves also do not require a medium for propagation, as they consist of oscillating electric and magnetic fields. Surface waves are a combination of both longitudinal and transverse waves and also require a medium to propagate.

3. A set of integers can be classified as positive, negative, or zero. Which of the following statements about multiplying positive and negative integers is ALWAYS true?

A. The product will always be positive.
B. The product will always be negative.
C. The product will depend on the specific positive and negative numbers used.
D. Positive and negative integers cannot be multiplied

Correct answer: B

Rationale: Rationale: When multiplying a positive integer by a negative integer, the product will always be negative. This is a fundamental rule of arithmetic. The sign of the product is determined by the rule that states that a positive number multiplied by a negative number results in a negative number. Therefore, the statement that the product will always be negative is always true when multiplying positive and negative integers.

4. Which of the following blood vessels carries oxygenated blood from the lungs back to the left atrium of the heart?

A. Pulmonary artery
B. Pulmonary vein
C. Aorta
D. Inferior vena cava

Correct answer: B

Rationale: The correct answer is B: Pulmonary vein. The pulmonary vein is the blood vessel that carries oxygenated blood from the lungs back to the heart. Oxygenated blood flows from the lungs through the pulmonary veins to the left atrium of the heart, where it is then pumped out to the rest of the body through the aorta. The pulmonary artery, on the other hand, carries deoxygenated blood from the heart to the lungs for oxygenation. The aorta is the largest artery in the body and carries oxygenated blood from the heart to the rest of the body. The inferior vena cava carries deoxygenated blood from the lower body back to the right atrium of the heart. Therefore, the correct choice is B, the pulmonary vein, as it specifically carries oxygenated blood from the lungs back to the left atrium of the heart.

5. Express 0.75 as a fraction.

A. 4/5
B. 3/4
C. 1/2
D. 1/4

Correct answer: B

Rationale: Decimals can be represented as fractions where the denominator is a power of 10 (in this case, 10 raised to the power of -1, or 1/10th). So, 0.75 is equivalent to 7/10. We can simplify this fraction by dividing the numerator and denominator by 5, resulting in 3/4.