Is a circuit breaker wired (a) in series with the device it is protecting, (b) in parallel, or (c) neither in series or in parallel, or (d) is it impossible to tell?

a) in series with the device it is protecting

Explanation:

A circuit breaker is an electrical device which is used to when one wants to avoid electrical surge through the circuit.

This electrical surge have the tendency of destroying the electrical devices or appliances which are likely part of the circuit.

The way a circuit breaker works is that the circuit have to open and as this happens the current passing through it is breached when it gets to the allowed current rate.

The circuit breaker is connected in series, since current dont change its flow in series rather in parallel connection.