As the urban heat island effect grows in a city, the city's are likely to experience higher temperatures than the suburbs.
a.
parks and green spaces
b.
downtown areas
c.
rural areas
d.
surrounding farmlands

The best and most correct answer among the choices provided by the question is the second choice "downtown areas"

An urban heat island (UHI) is an urban area or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities.

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B.  downtown areas

Explanation:

The urban heat island is a concept of urban areas getting hot and dry that created as a significant amount of heat and tends to be warmer than surrounding areas, and thus rural areas in contrast to this effect are cool and calm. The impact can be seen in the central business district or the downtown of the metropolitan cities and the air that gets warm in the afternoon is not able to escape and gets trapped inside the domes of the concrete city walls and owning to the lack of space this heat is unable to move out thus firms an island like effect.  For example, the metropolitan Delhi, Mumbai and the various other Indian cities have a high range of temperature that creates a heatwave like atmosphere to accumulate in the vicinity and the presence of the dust, ash and other pollutants combine to create this effect.

Ithink its deforestation.

How is this even a question?