Answer:
I believe the answer is "b". "During the experiment, the scientist has only one element, or variable, that is changed to test the hypothesis."
Explanation:
I remember from last year but I'm not totally sure. Good luck!
Answer:
They all have a certain amount of protons electrons and neutrons.
From what is given, double replacement is what it is
<span>Their outer shells are filled So much that they don't need to bond or react with any other atoms.</span>