Meaning: 'Shifting' means changing from one state or condition to another, in this case, moving towards renewable energy sources.

Wrong options:

• grafting: Grafting refers to a horticultural technique and does not relate to energy sources, making it contextually irrelevant.
• drafting: Drafting implies creating a preliminary version of something, which does not fit the context of changing energy sources.
• crafting: Crafting suggests making something skillfully, which does not convey the idea of changing energy sources as effectively as 'shifting'.

Correct answer: daunting

Explanation: The term 'daunting' is an adjective that describes something that seems difficult to deal with, which fits the context of the challenges faced in achieving a cleaner future. It matches grammatically and contextually with the sentence's sentiment about the obstacles ahead.

Meaning: 'Daunting' means intimidating or discouraging, indicating that the path to a cleaner future is filled with significant challenges.

Wrong options:

• daunted: 'Daunted' is the past participle form of the verb and does not fit grammatically as it would imply that the path itself has been intimidated, which is illogical.
• daunt: 'Daunt' is a verb and does not fit grammatically in this context where an adjective is required to describe the path.
• dauntless: 'Dauntless' means fearless, which contradicts the context of the challenges faced, making it an inappropriate choice.

Correct answer: obstacles

Explanation: The word 'obstacles' fits grammatically as a noun that refers to things that block one's way or prevent progress. It aligns contextually with the challenges mentioned in the sentence regarding the path to a cleaner future.

Meaning: 'Obstacles' means barriers or hindrances that make it difficult to achieve something, in this case, the transition to cleaner energy.

Wrong options:

• spectacles: 'Spectacles' refers to glasses or visual displays, which is irrelevant to the context of challenges in energy transition.
• tentacles: 'Tentacles' typically refers to appendages of certain animals and does not relate to the concept of barriers or challenges in this context.
• receptacles: 'Receptacles' are containers or holders, which does not fit the context of challenges or barriers.

Correct answer: fad

Explanation: The word 'fad' fits grammatically as a noun that refers to a temporary trend or craze. It aligns contextually with the idea that electric vehicles were once thought to be a passing trend, making it the most suitable choice.

Meaning: 'Fad' means a temporary fashion or trend that is popular for a short time, indicating that electric vehicles were initially seen as a short-lived phenomenon.

Wrong options:

• gad: 'Gad' is a verb meaning to move about aimlessly, which does not fit the context of describing a trend.
• tad: 'Tad' is an informal term meaning a small amount, which does not convey the idea of a trend or passing phenomenon.
• lad: 'Lad' refers to a young man or boy, which is completely unrelated to the context of trends in electric vehicles.