## Core Concept
The World No Tobacco Day is an annual global public health campaign marked by the World Health Organization (WHO). This day aims to highlight the risks associated with tobacco use and advocate for policies to reduce its consumption. It is observed on May 31st every year.

## Why the Correct Answer is Right
The correct answer, , corresponds to May 31st, which is the designated day for World No Tobacco Day. This day is significant because it provides an opportunity to raise awareness about the health risks associated with tobacco use, including lung cancer, heart disease, and chronic obstructive pulmonary disease (COPD). The WHO and other health organizations use this day to promote tobacco control policies and encourage individuals to quit smoking.

## Why Each Wrong Option is Incorrect
* **Option A:** - This option does not correspond to any recognized international health day related to tobacco control.
* **Option B:** - Similarly, this option does not match any known health awareness day focused on tobacco.
* **Option C:** - This is incorrect because September is not the month when World No Tobacco Day is observed.
* **Option D:** - This option is also incorrect for the same reason as options A, B, and C; it does not align with the date of World No Tobacco Day.

## Clinical Pearl / High-Yield Fact
A key point to remember is that World No Tobacco Day is observed on **May 31st** every year. This day is crucial for public health campaigns aimed at reducing tobacco use, which is a major risk factor for several chronic diseases.

## Correct Answer: C.