Meaning: 'Sprawled' refers to the way something has spread out over a large area in an untidy or irregular way.

Wrong options:

• concealment: Concealment refers to the act of hiding something, which does not fit the context of describing urban expansion.
• obstacles: Obstacles are barriers that impede movement, which does not describe the nature of cities themselves.
• suffocated: Suffocated means to be deprived of air or unable to breathe, which does not relate to the description of cities' growth.
• disproof: Disproof refers to evidence that contradicts a claim, which is unrelated to the context of urban sprawl.
• evidence: Evidence refers to information that supports a claim, which does not describe the state of cities.
• engaged: Engaged means involved or occupied, which does not fit the context of describing how cities have developed.

Correct answer: obstacles

Explanation: The term 'obstacles' refers to barriers that hinder progress or movement, which fits contextually as it describes the challenges to walking safely in urban environments. It is also grammatically correct as it serves as a noun in the sentence.

Meaning: 'Obstacles' are things that block one's way or prevent progress.

Wrong options:

• sprawled: Sprawled describes the state of cities, not the challenges to walking, making it contextually inappropriate here.
• concealment: Concealment refers to hiding something, which does not relate to the barriers to walking.
• suffocated: Suffocated describes a state of being deprived of air, which does not fit the context of walking challenges.
• disproof: Disproof refers to evidence that contradicts a claim, which is not relevant to the context of walking obstacles.
• evidence: Evidence refers to information supporting a claim, which does not describe the barriers to walking.
• engaged: Engaged means involved, which does not relate to the concept of obstacles in walking.

Correct answer: evidence

Explanation: The word 'evidence' serves as a noun that indicates proof or indication of something. In this context, it refers to the signs that demonstrate the decline in walkability, fitting grammatically and contextually as it highlights the situation regarding sidewalks.

Meaning: 'Evidence' refers to the available body of facts or information indicating whether a belief or proposition is true or valid.

Wrong options:

• sprawled: Sprawled describes the state of cities, which does not fit as a noun indicating proof or signs.
• concealment: Concealment refers to hiding something, which does not relate to the signs of walking issues.
• obstacles: Obstacles are barriers, not indicators or proof of the situation regarding sidewalks.
• suffocated: Suffocated describes a state of being deprived of air, which does not fit as a noun indicating proof.
• disproof: Disproof refers to evidence that contradicts a claim, which is not relevant to the context of sidewalk conditions.
• engaged: Engaged means involved, which does not relate to the concept of evidence in this context.

Correct answer: suffocated

Explanation: The term 'suffocated' is the past participle of 'suffocate,' which means to be deprived of air or unable to breathe. In this context, it metaphorically describes how walking has been hindered by other modes of transport, fitting grammatically and contextually as it conveys the impact on walking.

Meaning: 'Suffocated' means to be deprived of air, used here metaphorically to indicate that walking is being stifled or hindered.

Wrong options:

• sprawled: Sprawled describes the state of cities, which does not fit as a verb indicating the action of hindering walking.
• concealment: Concealment refers to hiding something, which does not relate to the act of hindering walking.
• obstacles: Obstacles are barriers, not actions that describe the state of walking.
• evidence: Evidence refers to proof or signs, which does not fit as a verb indicating the action of hindering.
• disproof: Disproof refers to evidence that contradicts a claim, which is not relevant to the context of walking being hindered.
• engaged: Engaged means involved, which does not relate to the concept of suffocation in this context.