Isotopes of the same element differ in their number of?

Neurons

Explanation:

Isotopes are atoms with different atomic masses which have the same atomic number. The atoms of different isotopes are atoms of the same chemical element; they differ in the number of neutrons in the nucleus.

? you expect us to answer this? ? this is your schoolwork, i don't think we can with this, i think it would considering being

c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current