Chuyển các câu chủ động sau sang dạng bị động.
1. In ancient times, people lit fires to use smoke as a signal over long distances.
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2. James Dyson invented Google Glass over a decade ago.
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3. People used radios to broadcast code messages during the Second World War.
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4. Most employers must pay the workers at least the federal minimum wage.
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5. A consumer group has found fake goats’ cheese for sale in supermarkets.
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6. Trans-fats which are bad for our hearts and cholesterol levels fill these low-fat foods.
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7. Have some scientists discovered a huge Blue whale colony in Sri Lanka?
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