Step 1: Order the stages in time.
Selye's model runs in a fixed order: alarm reaction, then resistance, then exhaustion. We need the one where the system is first switched on.
Step 2: Link the system to the order.
The activation of a body system as an answer to a new stressor must come at the very start, as the body has to alert itself before it can resist.
Step 3: Match with the options.
The alarm reaction stage is the first stage, so option (3) fits.
Step 4: Rule out the others.
Resistance is the coping phase that follows. Exhaustion is the last phase when the body can no longer cope. Burnout is a term from work stress and is not a stage of the model.
Step 5: Confirm.
Alarm means the body hears the warning and sends hormonal signals through the pituitary to the adrenal cortex.
Step 6: Quick recap of the reasoning.
We first understood what the question asks, then matched the key fact from the chapter with each option one by one, and finally dropped the options that belong to a different idea. This habit of linking every option to its own concept helps avoid careless slips in similar questions.
Final Answer:
The alarm reaction stage starts the adrenal-pituitary-cortex activity, so the answer is option (3).