Meaning: 'Sold' refers to smartphones that have been purchased by consumers.

Wrong options:

• made: 'Made' is the past participle of 'make,' which does not fit the context as it implies production rather than sales.
• exciting: 'Exciting' is an adjective that describes something that causes excitement, which does not relate to the action of selling.
• fears: 'Fears' is a noun that refers to feelings of anxiety, which does not fit grammatically or contextually in this sentence.
• saturation: 'Saturation' is a noun that refers to a state of being filled to capacity, which does not fit as it does not describe the action of selling smartphones.
• expensive: 'Expensive' is an adjective that describes high cost, which does not relate to the action of selling.

Correct answer: saturation

Explanation: The term 'saturation' refers to the point at which a market is no longer able to absorb more of a product. It fits contextually as it describes the market condition for iPhones among potential customers in developed countries.

Meaning: 'Saturation' indicates a state where demand has been met and no further growth is expected.

Wrong options:

• sold: 'Sold' is a past participle that refers to the action of selling, which does not fit as it does not describe a market condition.
• made: 'Made' is the past participle of 'make,' which does not relate to market saturation.
• continue: 'Continue' is a verb that implies ongoing action, which does not fit the context of describing a market state.
• fears: 'Fears' is a noun that refers to feelings of anxiety, which does not relate to market saturation.
• expensive: 'Expensive' is an adjective that describes high cost, which does not fit as it does not describe a market condition.

Correct answer: continue

Explanation: The word 'continue' is a verb that indicates ongoing action, which fits grammatically and contextually as it describes rival smartphone makers who are persistently challenging Apple.

Meaning: 'Continue' means to persist in an action or process.

Wrong options:

• sold: 'Sold' is a past participle that does not fit as it does not describe an ongoing action.
• made: 'Made' is the past participle of 'make,' which does not convey the idea of ongoing competition.
• fears: 'Fears' is a noun that refers to feelings of anxiety, which does not fit as it does not describe an action.
• saturation: 'Saturation' is a noun that refers to a market condition, which does not fit as it does not describe an action.
• expensive: 'Expensive' is an adjective that describes high cost, which does not relate to the action of challenging.

Correct answer: expensive

Explanation: The word 'expensive' is an adjective that describes the cost of devices. It fits grammatically and contextually as it contrasts with the powerful devices offered by rival smartphone makers.

Meaning: 'Expensive' means having a high price or cost.

Wrong options:

• sold: 'Sold' is a past participle that does not fit as it does not describe the cost of devices.
• made: 'Made' is the past participle of 'make,' which does not relate to the cost of devices.
• continue: 'Continue' is a verb that does not describe the cost of devices and does not fit in this context.
• fears: 'Fears' is a noun that refers to feelings of anxiety, which does not relate to the cost of devices.
• saturation: 'Saturation' is a noun that refers to a market condition, which does not fit as it does not describe cost.