1. Which vitamin is synthesized in the skin upon exposure to sunlight?

A. Vitamin A
B. Vitamin C
C. Vitamin D
D. Vitamin E

Correct answer: A

Rationale: The correct answer is Vitamin D (C). When the skin is exposed to sunlight, a compound in the skin is converted to Vitamin D. Vitamin A (A) is not synthesized in the skin but is found in foods like carrots and sweet potatoes. Vitamin C (B) is not synthesized in the skin either, but is found in citrus fruits and vegetables. Vitamin E (D) is not synthesized in the skin upon sunlight exposure, but is found in nuts and seeds.

2. What does the term "terminal velocity" refer to in physics?

A. Maximum velocity reached by an object in free fall
B. Velocity when the object is at rest
C. nstantaneous velocity of an object
D. Velocity only reached by heavy objects

Correct answer: a

Rationale: Terminal velocity is the constant velocity achieved by an object falling through the atmosphere when the force of air resistance equals the force of gravity.

3. Vaccines work by stimulating the immune system to develop:

A. A physical barrier against pathogens
B. An inflammatory response
C. Immunological memory to a specific pathogen
D. Phagocytes to engulf pathogens

Correct answer: C

Rationale: The correct answer is C: 'Immunological memory to a specific pathogen.' Vaccines work by introducing a harmless form of a pathogen or a piece of it to stimulate the immune system. This exposure triggers the production of antibodies and memory cells specific to that pathogen. These memory cells 'remember' the pathogen, allowing the immune system to respond more effectively and rapidly if exposed to the actual pathogen in the future. Options A, B, and D are incorrect because vaccines do not create a physical barrier, induce a general inflammatory response, or directly cause phagocytes to engulf pathogens; instead, vaccines enhance the immune system's ability to recognize and combat specific pathogens.

4. Electrons occupy specific energy levels around the nucleus, but not in fixed orbits. This concept is captured by the:

A. Bohr model
B. Quantum mechanical model
C. Lewis structure
D. Octet rule

Correct answer: B

Rationale: Quantum mechanical model. Unlike the Bohr model with its defined electron paths, the quantum mechanical model uses probability distributions to describe electron locations within energy levels.

5. Which structure in the respiratory system serves as a passageway for both air and food, with a flap-like structure that prevents food from entering the trachea during swallowing?

A. Larynx
B. Pharynx
C. Trachea
D. Bronchi

Correct answer: B

Rationale: The correct answer is B: Pharynx. The pharynx is a structure in the respiratory system that serves as a passageway for both air and food. It has a flap-like structure called the epiglottis, which prevents food from entering the trachea during swallowing. The larynx is commonly known as the voice box and is responsible for sound production. The trachea is a tube that carries air to and from the lungs, and the bronchi are the two main branches that lead from the trachea to the lungs. Therefore, the pharynx is the correct answer as it specifically fits the description provided in the question.

6. Which type of nuclear force is responsible for holding protons and neutrons together in the nucleus of an atom?

A. Electromagnetism
B. Gravity
C. Strong nuclear force
D. Weak nuclear force

Correct answer: C

Rationale: The incredibly powerful, strong nuclear force overcomes the repulsive electrostatic force between protons, binding them together and stabilizing the nucleus.