Choose your answer: Is "A lamp with the same rated lifetime but designed for 230 V would produce only around 12.8 lumens per watt, and a similar lamp designed for 30 volts (train lighting) would produce as much as 19.8 lumens per watt." a good answer to the question "How does filament size relate to voltage level?"
Possible answers:
[i] yes;
[ii] no;
[ii]