Which is the best explanation for why Toms technique works ?

The answer is b.the gaseous state is electrically positive, while the plasma state is electrically negative. 

The modern-day generator works on the principle of electromagnetic induction discovered by michael faraday in 1831-32. faraday discovered that the above flow of electric charges could be induced by moving an electrical conductor, such as a wire that contains electric charges, in a magnetic field.

I’m not sure about this question