1. Memory B cells and memory T cells are crucial for immunological memory. How does immunological memory enhance the immune response upon re-exposure to a pathogen?

A. It increases the production of the same ineffective antibodies.
B. It allows for a quicker and more robust immune response.
C. It suppresses the immune system to prevent overreaction.
D. It triggers a completely different immune response.

Correct answer: B

Rationale: Option B is correct because memory B cells and memory T cells retain information about a specific pathogen encountered before. Upon re-exposure to the same pathogen, these memory cells facilitate a faster and stronger immune response. Memory B cells quickly differentiate into plasma cells that produce antibodies more rapidly and in larger quantities than during the initial infection. Memory T cells can recognize the pathogen quickly and activate other immune cells to eliminate the threat efficiently. This allows the immune system to mount a quicker and more effective defense, potentially preventing the spread of the pathogen and reducing the severity of the infection.

2. Dandruff is caused by

A. Excessive sebum production (This can contribute to oily dandruff)
B. Bacterial infection (This can cause scalp folliculitis, not dandruff)
C. Overgrowth of a specific type of fungus on the scalp
D. Lack of proper skin hydration

Correct answer: C

Rationale: Dandruff is primarily caused by an overgrowth of a specific type of fungus called Malassezia on the scalp. This fungus feeds on the natural oils produced by the hair follicles, leading to an inflammatory response in some individuals, resulting in flaking and itching. Excessive sebum production can contribute to oily dandruff by providing more food for the fungus. Bacterial infections, such as scalp folliculitis, can cause symptoms similar to dandruff but are not the primary cause. Lack of proper skin hydration can contribute to dry scalp conditions but is not the main cause of dandruff.

3. A car is moving in a circle at constant speed. Which of the following is NOT true about its motion?

A. It has a constant centripetal acceleration
B. It has a constant tangential velocity
C. It experiences a force directed towards the center of the circle
D. It covers the same distance in equal time intervals along its circular path

Correct answer: B

Rationale: In circular motion at a constant speed, the car has a constant centripetal acceleration (choice A), experiences a force directed towards the center of the circle (choice C), and covers the same distance in equal time intervals along its circular path (choice D). However, the tangential velocity of an object in circular motion at a constant speed changes continuously as it moves around the circle, so it is not constant (choice B).

4. Which element is used in fire extinguishers to smother flames by displacing oxygen?

A. Nitrogen
B. Carbon dioxide
C. Helium
D. Argon

Correct answer: B

Rationale: Carbon dioxide extinguishes flames by depriving them of oxygen, preventing the chemical reaction that sustains the fire.

5. Which type of reaction is represented by the equation A + B â†’ AB?

A. Synthesis
B. Decomposition
C. Single Replacement
D. Double Replacement

Correct answer: a

Rationale: Synthesis reactions involve the combination of two or more substances to form a new compound.

6. What is the unit of measurement for momentum?

A. Newton-second (N·s)
B. Kilogram-meter (kg·m)
C. Joule (J)
D. Meter per second (m/s)

Correct answer: A

Rationale: Momentum is defined as the product of an object's mass and its velocity. The unit of mass is kilograms (kg) and the unit of velocity is meters per second (m/s). Therefore, the unit of momentum is kilogram-meter per second (kg·m/s). By Newton's second law of motion (F = ma), force is measured in Newtons (N), which is equivalent to kg·m/s². Therefore, multiplying the unit of force (N) by the unit of time (s) gives the unit of momentum as Newton-second (N·s).