Remember that a controlled variable is a variable that stays the same thoughout the experiment.
it wouldn't be a. because two different wires were used
the final length of the wax would be your dependent variable, so it wouldn't be c.
the thermal conductivity is the independent variable so it isn't d.
the original length of the wax was the same for both.
So B is your answer.
Answer:
The process where organisms naturally go and adapt to enviroment where they can most likely survive and produce more offspring.
Explanation:
Theory was first made by Charles Darwin and is now believed to be the main process that brings about evolution.