While shaping gold into ornaments, which part of the flame directly used by goldsmith?

1. Non-luminous
2. Luminous
3. Innermost zone
4. Whole flame

Correct Answer: (a) Non-luminous 

Explanation: A goldsmith uses the non-luminous zone (outermost zone) of a candle flame to melt gold and silver because it is the hottest part of the candle flame.