1. Which vitamin is crucial for calcium absorption and synthesized in the skin upon sun exposure?

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

Correct answer: C

Rationale: The correct answer is C: Vitamin D. Vitamin D is crucial for calcium absorption as it helps the body absorb calcium from the diet. When the skin is exposed to sunlight, it produces vitamin D. This is why sunlight is often referred to as the 'sunshine vitamin.' Vitamin A (choice A) is important for vision and immune function, but not specifically for calcium absorption. Vitamin C (choice B) is essential for collagen production and immune function, but not directly related to calcium absorption. Vitamin E (choice D) is an antioxidant that helps protect cells from damage, but it is not primarily involved in calcium absorption like vitamin D.

2. The number of protons in the nucleus of an atom determines its:

A. Mass number
B. Atomic number
C. Isotope
D. Valence electron count

Correct answer: B

Rationale: The atomic number (Z) equals the number of protons in the nucleus and uniquely identifies an element. Mass number (A) includes both protons and neutrons, isotopes have different neutron numbers, and valence electrons are involved in bonding, not atomic identity.

3. Electroencephalography (EEG) measures electrical activity in the brain, primarily reflecting the activity of:

A. Neurons
B. Astrocytes
C. Oligodendrocytes
D. Microglia

Correct answer: A

Rationale: The correct answer is A: Neurons. Electroencephalography (EEG) measures the electrical activity in the brain, which is primarily generated by the neurons. Neurons are the main cells responsible for transmitting electrical signals in the brain, making them the key source of the brain's electrical activity. Astrocytes, oligodendrocytes, and microglia are important supporting cells in the brain but do not generate the electrical impulses that EEG measures. Therefore, the correct choice is A: Neurons.

4. Which statement accurately describes the periodic trends in atomic radius?

A. Increases down a group and decreases across a period
B. Decreases down a group and increases across a period
C. Remains constant throughout the table
D. Fluctuates unpredictably based on individual elements

Correct answer: A

Rationale: Moving down a group, additional electron shells increase the distance from the nucleus, leading to larger atomic radii. Moving across a period, the number of electron shells remains constant, but the increasing nuclear charge pulls electrons closer, resulting in smaller radii.

5. A decorative globe has a diameter of 25cm. What is its total surface area?

A. 1570 sq cm
B. 1963 sq cm
C. 2513 sq cm
D. 3142 sq cm

Correct answer: B

Rationale: Use the formula for surface area of a sphere: 4 * Ï€ * (radius)^2, where radius is half the diameter. Calculate the radius (12.5cm) and substitute: 4 * Ï€ * (12.5cm)^2 â‰ˆ 1963 sq cm.