Concept:World Environment Day is a United Nations-designated day to promote global awareness and action for environmental protection.
Explanation:It is celebrated annually on June 5th.
The United Nations General Assembly established it in 1972, on the first day of the Stockholm Conference on the Human Environment.
This date was chosen to mark the start of that landmark conference.
Each year, a different theme is adopted by governments, organisations, and communities worldwide to encourage environmental action.
The other options – March 21, April 22, and October 16 – correspond to other international observances, not World Environment Day.
Answer:D. June 05