Answer:
Parallel
Step-by-step explanation:
If you imagine a current flowing through the circuit, when the current enters the headlight circuit, it has two branch into two parts. you can think of current as moving electrons and at the headlight branch, every electron will have to either go left or right. Because both headlights look exactly same, half of the electrons go left and half go right. So the current gets divided into two equal halves flowing through each headlight.