Meaning: 'Events' refers to occurrences or happenings, particularly those that can impact the environment.

Wrong options:

• possessions: 'Possessions' refers to items owned, which does not relate to occurrences affecting the environment.
• intentions: 'Intentions' refers to plans or aims, which does not fit the context of natural occurrences or human actions.
• changes: 'Changes' is a plural noun that refers to alterations, but it does not describe the source of substances being added to the environment.
• aspects: 'Aspects' refers to different features or parts, which does not fit as a source of substances.
• processes: 'Processes' refers to series of actions or steps, which does not describe events that add substances to the environment.
• stages: 'Stages' refers to phases in a process, which does not relate to the natural occurrences affecting the environment.

Correct answer: changes

Explanation: The term 'changes' is a plural noun that accurately describes the alterations in the environment caused by the substances mentioned, fitting both grammatically and contextually.

Meaning: 'Changes' refers to modifications or alterations in the state of something, in this case, the environment.

Wrong options:

• possessions: 'Possessions' refers to items owned, which does not relate to alterations in the environment.
• events: 'Events' refers to occurrences, which does not describe the impact on the environment directly.
• intentions: 'Intentions' refers to plans or aims, which does not fit the context of environmental alterations.
• aspects: 'Aspects' refers to features or parts, which does not describe the modifications occurring in the environment.
• processes: 'Processes' refers to series of actions, which does not accurately describe the changes in the environment.
• stages: 'Stages' refers to phases in a process, which does not relate to the changes occurring in the environment.

Correct answer: aspects

Explanation: The word 'aspects' is a plural noun that refers to different features or dimensions of the environment, fitting grammatically and contextually as it describes the areas affected by the substances.

Meaning: 'Aspects' refers to different parts or features of something, in this case, the environment.

Wrong options:

• possessions: 'Possessions' refers to items owned, which does not relate to features of the environment.
• events: 'Events' refers to occurrences, which does not describe the features of the environment.
• intentions: 'Intentions' refers to plans or aims, which does not fit the context of environmental features.
• changes: 'Changes' refers to modifications, which does not describe the features of the environment directly.
• processes: 'Processes' refers to series of actions, which does not accurately describe the features of the environment.
• stages: 'Stages' refers to phases in a process, which does not relate to the features of the environment.

Correct answer: processes

Explanation: The term 'processes' is a plural noun that refers to the series of actions or changes in the life of animals and plants, fitting grammatically and contextually in the sentence.

Meaning: 'Processes' refers to series of actions or changes that occur in living organisms.

Wrong options:

• possessions: 'Possessions' refers to items owned, which does not relate to the life functions of animals and plants.
• events: 'Events' refers to occurrences, which does not describe the life functions of organisms.
• intentions: 'Intentions' refers to plans or aims, which does not fit the context of biological functions.
• changes: 'Changes' refers to modifications, which does not accurately describe the series of actions in life processes.
• aspects: 'Aspects' refers to features or parts, which does not relate to the actions or changes in life processes.
• stages: 'Stages' refers to phases in a process, which does not accurately describe the ongoing actions in the life of organisms.