What is a factor that affects the outcome of an expirement?

What's the waste product of electrons and pyruvate combining in fermentation?  

The ruiz family is exchanging euros for us dollars. the exchange rate is 1 euro equals 1.35261 usd. since the ruiz family knows that usd are stated to the nearest hundredth of a dollar, they used the conversion ratio

How energy flows through each level in this energy pyramid. is all the matter and energy from one level transferred to the next level?