A.I. Explanation:

Correct answer: uneconomic

Explanation: The term 'uneconomic' fits grammatically as it describes the state of being not profitable or not worth the cost, which aligns with the context of fuel sources potentially becoming too expensive to obtain. This word is an adjective that modifies the implied subject of fuel sources, making it contextually appropriate.

Meaning: 'Uneconomic' means that something is not financially viable or profitable, indicating that obtaining certain fuel sources may not be worth the expense.

Wrong options:

• envisaged: 'Envisaged' means to imagine or foresee something, which does not fit the context of describing the economic viability of fuel sources.
• reluctant: 'Reluctant' describes a feeling of unwillingness, which does not apply to the context of fuel sources becoming difficult to obtain.
• greater: 'Greater' is a comparative adjective that does not logically fit in this context, as it does not describe the economic aspect of fuel sources.

Correct answer: provide

Explanation: The verb 'provide' is grammatically correct as it indicates the action of supplying or making available, which is contextually relevant to renewable energy sources supplying electricity. It fits the sentence structure perfectly as it follows the subject 'renewable energy sources'.

Meaning: 'Provide' means to supply or make available, indicating that renewable energy sources are sources of electricity.

Wrong options:

• retrode: 'Retrode' is not a standard English word and does not fit grammatically or contextually in this sentence.
• rode: 'Rode' is the past tense of 'ride' and does not make sense in the context of energy sources supplying electricity.
• divide: 'Divide' means to separate into parts, which does not fit the context of energy sources supplying electricity.

Correct answer: fossil

Explanation: The word 'fossil' is an adjective that correctly describes 'fuels', referring to fossil fuels like coal, oil, and natural gas. This fits grammatically and contextually as it contrasts with renewable energy sources, highlighting their environmental benefits.

Meaning: 'Fossil' refers to fossil fuels, which are energy sources derived from ancient organic matter, known for their environmental impact.

Wrong options:

• real: 'Real' does not specifically describe a type of fuel and is too vague for this context.
• raw: 'Raw' typically refers to something in its natural state and does not accurately describe fossil fuels in this context.
• royal: 'Royal' pertains to monarchy and does not relate to fuel types, making it irrelevant in this context.