Answer:
It is mentioned that the student is mixing chemicals A and B and observes the time taken for the color to change. However, in the experiment, it is noticed that the student has repeated the procedure five times and each time he or she is modifying the concentration of chemical B. Thus, it is clear that the concentration of chemical B is the independent variable in the experiment. An independent variable is illustrated as the variable, which is controlled or modified in the experiment.
Atom is a neutral element found in nature without any charge. In other words, it has same number of Protons and electrons, whereas ion is a charged thing, either positive or negative. We can find their charge by:
Charge = Number of Protons - Number of Electrons
Hope this helps!
The answer would be B the transfer of electrons from one atom to another
