Question

必须要采取行动来阻止疾病的传播。

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Answer

Action must be taken to prevent the spread of the disease.

【解析】

根据句意可知此句是含有情态动词must的被动语态，其构成：sth. must be done，以及是动词不定式作目的状语。短语take action：采取行动；阻止疾病的传播：prevent the spread of the disease。故答案为“Action must be taken to prevent the spread of the disease.”。