<h2>Answer:</h2>
Option C is correct.
C. 5 kilocalories
<h2>Explanation:</h2>
Only a little amount of energy as 10% is transferred to the next trophic level. This is called 10% rule. So, in this case as the energy available at the secondary trophic level is 50 kilocalories and 10% of it is transferred into the tertiary level so it would be 5 kilocalories.
The amount of oxygen that mixes with the gas stream effects the intensity of the combustion reaction in Bunsen burner. The correct option among all the options that are given in the question is the last option or option "C". The increase in the amount of air mix will result in a flame that has a higher temperature.