B. One
because an independent variable is something you change. So in a scientific experiment you only change one thing. If you happen to change more than one thing then the test becomes unfair therefore you should repeat and make sure that only one thing is changed this time.
Answer:
try to solve it on a paper
Answer:
I believe the answer is d
Has varied greatly over time
Darwin’s theory and the flow of genetic information and how we evolves for example the primates this is an example of evolution. It is the progress of mankind and for creatures
