A.I. Explanation:

Correct answer: shape

Explanation: The word 'shape' is a verb that fits grammatically in the sentence, indicating how plants influence or form our environment. It aligns with the context of discussing the role of plants in the biosphere and their impact on the environment.

Meaning: To 'shape' means to influence or determine the form or character of something.

Wrong options:

• degradation: 'Degradation' is a noun that refers to the process of something being damaged or deteriorated, which does not fit grammatically or contextually in this sentence.
• protection: 'Protection' is a noun that implies safeguarding, which does not convey the active role plants play in influencing the environment.
• simplify: 'Simplify' is a verb that means to make something easier to understand, which does not relate to the context of how plants affect the environment.
• power: 'Power' is a noun that refers to the ability to do something or act in a certain way, but it does not fit the grammatical structure of the sentence as it lacks a direct action related to the environment.
• source: 'Source' is a noun that indicates a point of origin, which does not fit the verb form needed in this context.

Correct answer: degradation

Explanation: The term 'degradation' is a noun that fits grammatically and contextually, referring to the decline or deterioration of the environment, which is one of the major challenges mentioned in the text.

Meaning: 'Degradation' refers to the process of something being damaged or reduced in quality, particularly in an environmental context.

Wrong options:

• shape: 'Shape' is a verb that does not fit grammatically as a noun in this context, and it does not relate to the challenges facing humanity.
• protection: 'Protection' is a noun that implies safeguarding, which does not accurately describe the challenges of environmental decline.
• simplify: 'Simplify' is a verb that means to make something easier, which does not relate to the context of environmental challenges.
• power: 'Power' is a noun that refers to the ability to do something, but it does not fit the context of environmental issues as a challenge.
• source: 'Source' is a noun that indicates a point of origin, which does not align with the context of environmental challenges.

Correct answer: source

Explanation: The word 'source' is a noun that fits grammatically in the sentence, indicating that plants are a fundamental origin of energy production. This aligns with the context of discussing the role of plants in energy and food production.

Meaning: A 'source' is a point of origin or supply from which something is obtained.

Wrong options:

• degradation: 'Degradation' is a noun that refers to decline or deterioration, which does not fit the context of describing plants' role in energy production.
• protection: 'Protection' is a noun that implies safeguarding, which does not relate to the context of energy production from plants.
• shape: 'Shape' is a verb that does not fit grammatically as a noun in this context, and it does not describe the role of plants in energy production.
• simplify: 'Simplify' is a verb that means to make something easier, which does not relate to the context of plants as a source of energy.
• power: 'Power' is a noun that refers to the ability to do something, but it does not fit the grammatical structure needed to describe plants' role.