【C13】A．whenB．ifC．unlessD．whereas

【C13】A．thoughB．as ifC．ifD．as

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【C7】A．WhenB．LestC．UnlessD．If

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【C13】A．althoughB．ifC．whenD．since

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【C9】A．WhileB．IfC．UnlessD．Meanwhile

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【C9】A．whenB．ifC．untilD．after

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【C13】A．whenB．ifC．beforeD．since

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Doctors won t operate on the patient______absolutely necessary.A．whenB．ifC．unlessD．though

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