How are metro trains powered?

Related questions

1. Is Delhi Metro safe for tourists?
2. How much is St Petersburg metro?
3. How much is it to ride the Metro?
4. What is the fastest bullet train?
5. Does Metro take cash?
6. Do you need a tap card to ride the Metro?
7. How fast do express trains go?
8. How do Metro tokens work?
9. How do I check my balance on my TAP card Metro?
10. How fast do coal trains go?

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