4 May is observed as -

Answer: Option D

International Firefighter's Day is observed every year on 4 May. It was instituted on 4 January, 1999 after a proposal via emailed out across the world due to the deaths of five firefighter's in a bushfire in Australia. Therefore, this day is observed to recognise and honour the sacrifices that firefighter's make to ensure that their communities and environment are as safe as possible.