Answer:
Negative controls are particular samples included in the experiment that are treated the same as all the other samples but are not expected to change due to any variable in the experiment.
Step-by-step explanation:
Answer:
20%
Step-by-step explanation:
If you see they say that the number decreased is 10% each and they say it two times. we could see that the missing number is as big as the length of two 10% together, so if you add them two you get 20%.