1. After exposure to a pathogen, the immune system develops memory. What type of immune cell is responsible for this immunological memory?

A. B cells
B. T cells (specifically memory T cells)
C. Phagocytes
D. Natural killer cells

Correct answer: B

Rationale: The correct answer is A: "B cells." B cells are responsible for generating immunological memory after exposure to a pathogen. When B cells encounter a pathogen, they differentiate into memory B cells, which can quickly recognize and respond to the pathogen upon subsequent exposure. These memory B cells are crucial for mounting a faster and more effective immune response, leading to a quicker clearance of the pathogen. T cells, phagocytes, and natural killer cells play important roles in the immune response, but specifically, memory B cells are responsible for immunological memory.

2. The author's attitude towards history seems to be

A. indifferent and neutral, presenting it as an objective field of study.
B. critical and dismissive, questioning its practical applicability in the present.
C. enthusiastic and optimistic, highlighting its potential to guide the future.
D. pessimistic and cautious, emphasizing the risk of repeating past mistakes.

Correct answer: C

Rationale: The passage's overall tone highlights the value and utility of history, showcasing its potential to inspire and guide us, suggesting an optimistic and encouraging view.

3. What is the principle behind the phenomenon of refraction, where waves bend when entering a new medium?

A. Change in wavelength
B. Change in frequency
C. Change in wave speed
D. None of the above

Correct answer: C

Rationale: Refraction occurs because of the change in wave speed as it enters a new medium, causing the wavefront to bend and change direction.

4. Which of the following situations represents work being done on an object?

A. Pushing against a wall without moving it
B. Carrying a heavy object without lifting it
C. Lifting a box to place it on a shelf
D. Holding a book stationary in your hand

Correct answer: c

Rationale: Work is done when a force is applied to move an object over a distance.

5. What is the formula to calculate work?

A. Work = Force Ãƒâ€” Distance
B. Work = Mass Ãƒâ€” Velocity
C. Work = Power Ãƒâ€” Time
D. Work = Energy ÃƒÂ· Time

Correct answer: a

Rationale: Work is calculated by multiplying force exerted on an object by the distance the object moves in the direction of the force.

6. What happens to the potential energy of an object when it is lifted higher above the ground?

A. Potential energy decreases
B. Potential energy remains the same
C. Potential energy increases
D. Potential energy becomes zero

Correct answer: C

Rationale: When an object is lifted higher above the ground, its potential energy increases because the higher the object is lifted, the greater its potential energy due to the increased distance from the ground. This is in accordance with the formula for gravitational potential energy, which is PE = mgh, where m is the mass of the object, g is the acceleration due to gravity, and h is the height above the reference point.