Decide which structure is used in the following sentences. first, i wash my face. next, i brush my teeth. then, i put on my pajamas. at last, i lay down. finally, i fall asleep.

C) Chronological order.

Explanation: Chronological order is a method of organization that consists in the arrangement of things following one after another in time (in the order they happen). In the given paragraph we can see a list of steps that the speaker does before going to sleep. As we can see, he/she describes the things she/he does in the order that she/he does them. So the used structure is chronological.

I would say sequential or chronological.

(especially of liquids, gases, or electricity) to move in one direction, especially continuously and easily:
Lava from the volcano was flowing down the hillside.
Many short rivers flow into the Pacific Ocean.
The river flows through three counties before flowing into the sea just south of here.
With fewer cars on the roads, traffic is flowing (= moving forward) more smoothly than usual.
Hope i helped