a large funnel a screen filter a horseshoe magnet a magnifying glass
I gave my students this multiple choice question: Which is most useful to a student who is separating aluminum screws from steel screws?

Only one answer is correct among these 4 choices:
- a large funnel
- a screen filter
- a horseshoe magnet
- a magnifying glass

Could you tell me which one is correct?

a horseshoe magnet