The match! Then use it to light the oil lamp or the candle.
Try this: Which is the word in English that has nine letters, and remains a word at each step even when you remove one letter from it, right up to a single letter remaining. Check out the answer here.
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Of interest, Ben Minett, a college student, invented The Riddle Game and put it online with the help of developer BMS Electronics. The free app provides users with 125 riddles and has been downloaded 10,000 times... but nobody can solve all its fiendish riddles! Try solving some here.