Step 1: Understanding the Question:
This question tests knowledge of environmental awareness days.
Step 2: Detailed Explanation:
World Ozone Day is celebrated on 16th September.
It commemorates the signing of the Montreal Protocol (1987).
11th September (A): Not correct.
11th October (B): Not correct.
16th October (D): Not correct.
Thus, the correct answer is 16th September.
Step 3: Final Answer:
Thus, World Ozone Day is celebrated on 16th September, which corresponds to option (C).
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