The industrial revolution damaged our ecosystem
I’m not sure how to answer your question if there is no link to the video?
If a bacterium cannot use citrate agar will not change its color (stays green). On the other hand, if bacteria have the ability to use citrate, the medium will change its color from green to blue.
This happens because citrate agar contains pH indicator such as bromothymol blue which transforms from green to blue in alkaline conditions.
For me i’ll say the answer is A bit i might be wrong so do what’s best for you
