Step 1: Understanding the Concept:
When a baby chokes on an object, the rescuer follows a fixed drill, and the order of the steps actually matters for the drill to work safely.
Step 2: Key Formula or Approach:
The drill for an infant always tries physical force to dislodge the object before ever putting fingers in the mouth, because looking or sweeping too early, before the object has been pushed loose, risks pushing it deeper instead of out.
Step 3: Detailed Explanation:
The rescuer starts with back blows: holding the infant face down on the forearm, with the head lower than the body, and striking the back between the shoulder blades up to five times.
If the object has still not come out, the rescuer flips the infant face up and gives chest thrusts, pressing the lower chest sharply up to five times, similar to the hand position used for chest compressions.
Only now does the rescuer open the mouth and use a tongue-jaw lift to look for the object, removing it by hand only if it can actually be seen; this comes last because searching blindly at the start could shove an unseen object further down the airway.
This gives the working order as back blows, then chest thrust, then tongue-jaw lift, written as 3, 1, 2. Any sequence that puts the tongue-jaw lift first, or a chest thrust before the back blows, breaks this safety order.
Step 4: Final Answer:
\[ \boxed{3,\ 1,\ 2\ (\text{Back blows} \to \text{Chest thrust} \to \text{Tongue-jaw lift})} \]