mark+scheme+from+Michael


 * 1) air-detector/ gas detector/ sensor, Switch or reasonable answer, temperature sensor
 * 2) **Coordination** of different operations, pull alarm if reading exceeds a threshold, constant **polling** of different sensors.
 * 3) Face recognition or finger print. ; camera, processor. ; It checks something you are instead of something you have or own, the most secure approach, require nothing but the person, reasonable answer is acceptable