Detailed Instructions: You are given a list of queries separated by new line. Your job is to answer with the query that is the most well-formed or well-structured query in terms of grammar, punctuations, or spelling errors.
Q: What is scientific meaning of constant ?
When were cameras envented ?
How many litres in a 40 pounds propane tank ?
How many floors are ther in the Murkey cave ?
A:
How many litres in a 40 pounds propane tank ?