Nanoparticles used to remove E. coli bacteria from water

The same question, asked 2 times: 20 Apr 2025 S2, 12 May 2026 S2. Every wording below, oldest first.

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Question 1
20 Apr 2025 S2
71 $Which of the following is effectively used to remove E. coli bacteria from water?$
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Question 2
12 May 2026 S2
18 $E.coli bacteria from water can be effectively removed by using-$
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