Meaning: Heat refers to high temperatures, particularly in urban areas during summer.

Wrong options:

• biodiversity: Biodiversity refers to the variety of life in a particular habitat, which does not fit the context of reducing temperature.
• pollution: Pollution is the presence of harmful substances in the environment, which is not directly related to the temperature aspect discussed here.
• population: Population refers to the number of people living in an area, which does not relate to the concept of heat reduction.
• gardening: Gardening is an activity related to planting and maintaining plants, which does not fit as a noun describing a condition affected by trees.
• recreational: Recreational refers to activities done for enjoyment, which does not pertain to the temperature context.

Correct answer: stormwater

Explanation: The term 'stormwater' is a noun that refers to water that originates from precipitation events. It fits grammatically and contextually as it relates to runoff that can be managed by green roofs.

Meaning: Stormwater is the water that flows over surfaces during and after rain, which can lead to flooding if not managed properly.

Wrong options:

• biodiversity: Biodiversity does not relate to water runoff and is not a suitable term in this context.
• pollution: Pollution refers to contaminants in the environment, which does not specifically address the issue of runoff from storms.
• population: Population does not relate to water management and is irrelevant in this context.
• gardening: Gardening is an activity and does not pertain to the concept of water runoff.
• recreational: Recreational refers to leisure activities and does not connect to stormwater management.

Correct answer: gardening

Explanation: The word 'gardening' is a gerund that describes the activity of cultivating plants, which fits grammatically and contextually as it relates to community projects that engage residents.

Meaning: Gardening refers to the practice of growing and cultivating plants, often in a community setting.

Wrong options:

• biodiversity: Biodiversity refers to the variety of life and does not fit as an activity that encourages local engagement.
• pollution: Pollution is not an activity and does not relate to community engagement in a positive manner.
• population: Population does not describe an activity and is irrelevant in the context of community projects.
• stormwater: Stormwater is a noun related to water runoff and does not fit as an activity that encourages engagement.
• recreational: Recreational refers to activities for enjoyment but does not specifically relate to the act of gardening.

Correct answer: population

Explanation: The term 'population' is a noun that refers to the number of people living in an area. It fits grammatically and contextually as it addresses the challenge of managing growth in urban settings.

Meaning: Population refers to the total number of individuals inhabiting a particular area, which is relevant to urban planning.

Wrong options:

• biodiversity: Biodiversity does not relate to the challenge of growth in urban areas and is not suitable in this context.
• pollution: Pollution refers to environmental contaminants and does not address the issue of population growth.
• gardening: Gardening is an activity and does not pertain to the concept of population growth.
• stormwater: Stormwater is related to water management and does not fit the context of discussing urban growth challenges.
• recreational: Recreational refers to leisure activities and does not relate to the concept of population growth.