Current always returns to the:

a) positive battery terminal
b) negative battery terminal

Current always returns to the negative terminal.

Explanation:

Current flows from a positive to a negative terminal. It is due to the flow of negative electrons to positive side. The current flows from a high potential to a low potential. There is high concentration of electrons at the positive terminal and low concentration at the negative terminal. When the circuit is complete the electrons move from a high concentration to low concentration i.e; from positive terminal to negative terminal.

resonant frequency