Chuyển các câu sau sang thể phủ định 
1.They are going to announce the exam results tomorrow.
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2.They should widen the road at this point.
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3.An expert should check these machines reqularly.
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4.We'll have to repair the roof before the rainy season comes.
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5.They ought to white-wash the building for the celebration.
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6.You must attach a birth certificate to the application.
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7.You shought inform the school of yuor change of addres.
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8.They will close the factory until further notice.
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