Final answer:
Characteristics A and B accurately describe a series circuit, where all components are connected in a single pathway, and the failure of one component affects the entire circuit. Options C and D are incorrect because adding bulbs in a series circuit decreases brightness and electrons do not have multiple pathways in a series circuit.
Step-by-step explanation:
A series circuit has distinct characteristics that can be used to describe it. Options A and B correctly describe a series circuit. Specifically, A) All of the parts of a series circuit—power source, wires, and devices—are connected along the same pathway, which means that there is only one path for the electrons to travel through the circuit. Additionally, B) If one device in a series circuit burns out or is disconnected, the entire circuit is broken. This is because in a series circuit, all components are connected end-to-end in a single path, so the failure of any single component interrupts the flow of current throughout the entire circuit.
Options C and D do not describe a series circuit. C) If there are many bulbs in a circuit with a battery (cell), it is very likely that the light will be brighter with each additional bulb, is incorrect because in a series circuit, adding more bulbs actually causes each bulb to be dimmer due to the increased resistance and consequent reduction in current flow through each bulb. D) The electrons have multiple pathways to travel. is also incorrect as this is a defining feature of a parallel circuit, not a series circuit.
In summary, in a series circuit, the same current flows through all components, but the voltage drop across each component can vary based on the component's resistance, and the total of all individual voltage drops equals the voltage of the power source.