<span>The only way to test a particular variable for sure is to leave all other variables constant, and if a change in ONE variable creates an overall change, then you know that that variable caused it. But if you change 2 variables, and something changes, you don't know which one changed it for sure. </span>
C. by observing them in their habitats
Ex: The Galapagos Islands. Darwin went their to study the flora and fauna in their natural habitat.
This might be wrong and i am sorry if it wrong but i think it is A. a planet that produced flowers and seeds on tall stalks and i am sorry again if its wrong
Answer:
A
Explanation:
If Im wrong pls correct me, I hope it will help