It means to change, and form means shape. So to transform is to change shape.
The answer is D, reactant.
Isotopes of elements have same atomic numbers and different mass number(atomic masses).
(I know this is late so hopefully other people find it helpful)
<u>Answer</u>: Solid Cu
Since this is a <u>voltaic cell</u>:
<u>Copper</u> is the cathode, therefore having a positive charge.
<u>Zinc</u> is the anode, therefore having a negative charge.
(Also, I took the exam and it's correct; good luck everyone!)