Final answer:
The 'Investigate' step of the S.I.R.E.N. acronym when encountering an emergency vehicle involves checking your rear-view mirror.
Step-by-step explanation:
The correct answer is b) Check your rear-view mirror.
When you encounter an emergency vehicle, the 'Investigate' step of the S.I.R.E.N. acronym involves checking your rear-view mirror. This allows you to assess the situation and determine the best course of action. It is important to be aware of the emergency vehicle's proximity and movement so you can safely give them the right of way.