Meaning: 'Fluid' means something that is not stable or fixed, indicating that social bonds in urban environments can change easily over time.

Wrong options:

• discriminatory: 'Discriminatory' implies unfair treatment based on characteristics, which does not fit the context of social bonds being changeable.
• interconnected: 'Interconnected' suggests strong connections, which contradicts the idea of bonds being less reliable in urban settings.
• feasible: 'Feasible' means possible or practical, which does not relate to the nature of social bonds in this context.

Correct answer: ironically

Explanation: The word 'ironically' fits well as it introduces a contrast between the expectation of community in crowded places and the reality of isolation, aligning with the overall sentiment of the passage.

Meaning: 'Ironically' indicates a situation that is contrary to what one would expect, highlighting the paradox of feeling isolated in a crowd.

Wrong options:

• nervously: 'Nervously' implies anxiety, which does not relate to the context of isolation amid crowds.
• collectively: 'Collectively' suggests togetherness, which contradicts the idea of isolation.
• fondly: 'Fondly' implies affection, which does not fit the context of discussing isolation.

Correct answer: affluent

Explanation: The word 'affluent' accurately describes wealthy neighborhoods, fitting the context of socioeconomic inequalities and contrasting with underprivileged areas, thus maintaining grammatical and contextual coherence.

Meaning: 'Affluent' means having a lot of money or wealth, indicating neighborhoods that are economically well-off.

Wrong options:

• resourceful: 'Resourceful' refers to the ability to find quick and clever ways to overcome difficulties, which does not describe a type of neighborhood.
• cooperative: 'Cooperative' suggests working together, which does not pertain to the economic status of neighborhoods.
• floral: 'Floral' relates to flowers and does not connect to the socioeconomic context of neighborhoods.

Correct answer: raise

Explanation: The word 'raise' is the correct form here as it is used in the context of posing questions, fitting grammatically as the subject is plural (challenges) and requires the base form of the verb.

Meaning: 'Raise' means to bring up or to cause to happen, in this case referring to questions about sustainability.

Wrong options:

• are raised: 'Are raised' is passive and does not fit the active construction needed in this context.
• raising: 'Raising' is a gerund form that does not fit the grammatical structure of the sentence.
• raises: 'Raises' is singular and does not agree with the plural subject 'challenges'.