1. The primary function of the respiratory system is to:

A. Maintain body temperature
B. Deliver oxygen to the bloodstream and remove carbon dioxide
C. Produce antibodies for the immune system
D. Break down food molecules for energy

Correct answer: B

Rationale: The correct answer is B: 'Deliver oxygen to the bloodstream and remove carbon dioxide.' The primary function of the respiratory system is to facilitate gas exchange. When we breathe in, oxygen is inhaled and transported to the bloodstream, where it is delivered to cells for energy production. Simultaneously, carbon dioxide, a waste product of cellular metabolism, is removed from the bloodstream and exhaled. This process is vital for sustaining life and maintaining proper oxygen levels in the body. The respiratory system does not primarily regulate body temperature, produce antibodies, or break down food molecules for energy, making options A, C, and D incorrect.

2. 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.

3. How does the stability of an atom's nucleus influence its radioactive decay?

A. Stable nuclei never undergo radioactive decay.
B. Unstable nuclei are more likely to decay through various processes.
C. Decay releases energy, making stable nuclei more prone to it.
D. The element's position on the periodic table determines its decay rate.

Correct answer: B

Rationale: Unstable nuclei are more likely to decay through various processes. The stability of an atom's nucleus is a key factor in determining whether it will undergo radioactive decay. Unstable nuclei have an excess of either protons or neutrons, leading to an imbalance in the nucleus. To achieve a more stable configuration, these nuclei will undergo radioactive decay by emitting particles or energy. Stable nuclei, on the other hand, are less likely to undergo radioactive decay as they have a balanced number of protons and neutrons.

4. Which property of a substance measures the amount of matter per unit volume?

A. Density
B. Mass
C. Weight
D. Volume

Correct answer: a

Rationale: Density is the property that measures the amount of matter (mass) per unit volume of a substance. It is calculated as mass divided by volume.

5. What is the main topic of the passage?

A. Benefits of bioremediation in cleaning oil spills.
B. Dangers of microplastics to marine ecosystems.
C. History of plastic production and its global impact.
D. Comparison of different waste management strategies.

Correct answer: B

Rationale: The passage focuses on the specific issue of microplastics in the marine environment and their harmful effects.

6. Which term refers to the resistance of a liquid to flow?

A. Density
B. Viscosity
C. Surface tension
D. Boiling point

Correct answer: B

Rationale: Viscosity is the term that refers to the resistance of a liquid to flow. It is a measure of how thick or sticky a fluid is, and it determines how easily a liquid can flow. Density (A) is a measure of how much mass is contained in a given volume, surface tension (C) is the property of a liquid that allows it to resist an external force due to the cohesive nature of its molecules, and boiling point (D) is the temperature at which a liquid changes to a vapor.