Meaning: 'Decades' means periods of ten years, indicating a significant length of time over which progress has been measured.

Wrong options:

• doubtful: 'Doubtful' is an adjective that describes uncertainty and does not fit as a noun to indicate a time period.
• destiny: 'Destiny' refers to a predetermined course of events and does not relate to a measurable time frame.
• dowry: 'Dowry' is a noun that refers to property or money brought by a bride to her husband on their marriage, which is irrelevant in the context of discussing time and progress.

Correct answer: ranging

Explanation: The word 'ranging' is a verb that indicates a variation or spectrum of values, which fits contextually as it describes the percentage of urban dwellers living in slums across different regions. It aligns with the grammatical structure of the sentence, which discusses a range of statistics.

Meaning: 'Ranging' means varying within certain limits, indicating that the percentage of slum dwellers differs from one area to another.

Wrong options:

• rotation: 'Rotation' refers to the act of turning around a center point and does not apply to the context of percentages.
• round: 'Round' can mean to make something circular or to approximate a number, which does not fit the context of describing varying percentages.
• remains: 'Remains' is a verb that suggests something continues to exist, which does not convey the idea of variation in percentages.

Correct answer: regions

Explanation: The word 'regions' is a plural noun that refers to specific areas or divisions, which fits grammatically and contextually as it describes the less developed areas being discussed. It aligns with the overall theme of the passage regarding urban populations.

Meaning: 'Regions' means specific areas or parts of a country or the world, indicating the geographical context of the discussion.

Wrong options:

• revenue: 'Revenue' refers to income generated, which does not relate to the context of geographical areas.
• repair: 'Repair' is a verb that means to fix something, which is irrelevant in the context of discussing populations and areas.
• restrict: 'Restrict' is a verb that means to limit or control, which does not fit the context of describing areas or populations.

Correct answer: environmental

Explanation: The word 'environmental' is an adjective that describes aspects related to the environment, fitting grammatically and contextually as it modifies 'sustainability.' It aligns with the theme of the passage regarding urban living conditions and sustainability indicators.

Meaning: 'Environmental' refers to anything related to the natural world and the impact of human activity on it, emphasizing the importance of sustainability.

Wrong options:

• enable: 'Enable' is a verb that means to make something possible, which does not fit as a descriptor for sustainability.
• envelope: 'Envelope' is a noun that refers to a flat paper container, which is irrelevant in this context.
• encompass: 'Encompass' is a verb meaning to include or cover, which does not fit grammatically as it does not modify 'sustainability' appropriately.

Correct answer: access

Explanation: The word 'access' is a noun that refers to the ability to obtain or make use of something, fitting grammatically and contextually as it describes the lack of availability of improved water supply. It aligns with the overall theme of discussing urban living conditions.

Meaning: 'Access' means the ability to enter or make use of something, in this case, referring to the availability of water supply.

Wrong options:

• applause: 'Applause' is a noun that refers to clapping in approval, which is irrelevant in the context of discussing water supply.
• archery: 'Archery' is a noun that refers to the sport of shooting arrows, which does not relate to the context of water supply.
• appears: 'Appears' is a verb that means to become visible or noticeable, which does not fit as a noun in this context.