Final answer:
The correct answer is 'A city' since it represents a specific area where living organisms interact with each other and with the physical surroundings, making it an example of an environment.
Step-by-step explanation:
An environment refers to the surrounding conditions in which an organism lives, which includes biotic (living) and abiotic (non-living) factors. In the context of the options provided, 'A city' (d) is an example of an environment because it is a specific area or region where living organisms, such as humans, animals, and plants, interact with each other and the physical surroundings like buildings, roads, and the atmosphere. Temperature (a) and humidity (c) are attributes of an environment, not environments themselves. 'The world' (b) is too broad a term and can encompass many environments, not a single one. An example of a healthy environment for a city includes elements such as water availability and a favorable climate. Moreover, the existence of life and ecosystems within a city, such as urban parks, rivers, and even the animal and plant life that adapt to urban conditions, contribute to the overall environment of that urban area.