Prelude in C Major, Bach

[superdominus]

I have just recently started practicing the prelude in C major from book I of the WTC. There's a footnote in my book about a measure that may be omitted. Its authenticity has not been verified. I'm sure you guys know which measure this is. I'm not sure whether should I play this measure or not. My teacher told me to play the measure. However, I don't want to play it if Bach didn't wrote it down, and in my opinion, omitting this measure makes that part more dramatic.

I am eager to hear your opinions on this measure. Do you play it or leave it out? 

[guendola]

It doesn't really matter! This "added" measure is there because nobody can tell if it belongs there or not. Learn it to please your teacher (and avoid unnecessary arguments) and leave it out at home

As a matter of fact, you should ask your teacher why he wants you to play it. These little insights into other people's thoughts help you develop your understanding of music, no matter how correct these thoughts are (not saying that your teacher is wrong here!) and that is the most valuable asset of a musician besides the physical abilitites to play instruments.