There are so many examples for that in different areas, like biology experiment carried out in our lab recently.
Here's one link:https://www.creative-biogene.com/support/Baculovirus-Efficient-Tool-for-Protein-Expression.html
B. Because a physical reaction is a change that can be seen. This particular situation is happening over a period of time, it isn’t something that happens instantly. Also I it would have been a chemical reaction, it would have mentioned something about the state of an element or the temperature or something along those lines.
Microbes as they tend to produce rapidly on a surface of other microbes such as bacteria and fungi.
