Final answer:
A magnet is the best tool for separating iron filings from sand.
Step-by-step explanation:
The best tool for separating iron filings from sand is a magnet.
When a magnet is moved over a mixture of iron filings and sand, the iron filings are attracted to the magnet and can be easily separated. This separation is based on the property of magnetism, where iron is a magnetic material that can be attracted by a magnet.
Using water, a pasta strainer, or filter paper would not be effective for separating iron filings from sand as they do not exploit the magnetic properties of iron.
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