**Core Concept**
World No Tobacco Day is an annual event observed globally to raise awareness about the risks associated with tobacco use and to promote actions for tobacco control. This awareness day is an initiative of the World Health Organization (WHO) to combat the global tobacco epidemic.

**Why the Correct Answer is Right**
The correct answer is 31st May because the WHO designated this day in 1987 to draw attention to the tobacco epidemic and its devastating health, environmental, and economic consequences. This day is an opportunity for governments, civil society, and individuals to come together and take concrete actions to reduce the global spread of tobacco use.

**Why Each Wrong Option is Incorrect**
**Option A:** May 1st is celebrated as May Day or Labor Day in many countries, and it has no relation to World No Tobacco Day.
**Option C:** August 1st is not a designated day for any global health awareness campaign related to tobacco control.
**Option D:** August 31st is not a recognized day for tobacco control efforts at the global level.

**Clinical Pearl / High-Yield Fact**
The global tobacco epidemic is responsible for over 7 million deaths each year, with more than 6 million of these deaths being directly attributed to tobacco use. This highlights the urgent need for tobacco control measures and increased awareness about the risks associated with tobacco use.

**✓ Correct Answer: B. 31st May**