Meaning: 'Requires' means to need something for a particular purpose, indicating that establishing a uniform poverty level is essential for accurate measurement.

Wrong options:

• replaces: 'Replaces' implies substitution, which does not fit the context of needing to establish a level; it suggests one thing taking the place of another, which is not the case here.
• restores: 'Restores' means to bring something back to a former condition, which is irrelevant in this context as it does not relate to the establishment of a poverty level.
• relies: 'Relies' suggests dependence on something, which does not convey the necessity implied in the sentence regarding establishing a uniform poverty level.

Correct answer: prices

Explanation: The word 'prices' is the most suitable choice as it directly relates to the cost of goods and services, which is essential for understanding the poverty line in different countries. It fits both grammatically and contextually within the sentence.

Meaning: 'Prices' refer to the amounts of money required to purchase goods and services, which is crucial for comparing poverty levels across countries.

Wrong options:

• rates: 'Rates' generally refer to a measure or quantity, often used in financial contexts, but does not specifically address the cost of goods and services as needed here.
• goods: 'Goods' refers to tangible products but does not encompass the broader concept of costs associated with purchasing, which 'prices' does.
• services: 'Services' refers to intangible offerings but lacks the comprehensive nature of 'prices' that includes both goods and services.

Correct answer: least

Explanation: The word 'least' is appropriate as it indicates the lowest level of development among countries, fitting grammatically and contextually with the description of the $1 per day level.

Meaning: 'Least' means the smallest amount or degree, indicating that the countries referred to are the least developed in terms of economic status.

Wrong options:

• less: 'Less' is a comparative term that does not fit grammatically in this context, as it requires a noun to follow, while 'least' serves as a superlative adjective.
• little: 'Little' implies a small quantity but does not convey the comparative sense needed here to describe the level of development.
• lack: 'Lack' refers to the absence of something, which does not fit the context of describing a level of development.

Correct answer: middle-income

Explanation: The term 'middle-income' accurately describes economies that fall between low and high income, fitting both grammatically and contextually within the sentence about poverty levels.

Meaning: 'Middle-income' refers to countries with moderate levels of income, indicating their economic status in relation to poverty measurement.

Wrong options:

• less-income: 'Less-income' is not a standard term used to describe economic status and does not fit grammatically or contextually in this context.
• high-income: 'High-income' refers to wealthier economies, which does not align with the context of the $2-per-day level being used for middle-income economies.
• more-income: 'More-income' is not a recognized term in economic classifications and does not fit the context of describing a specific category of economies.