**Core Concept**
The World Health Organization (WHO) has established global targets for oral health to improve the oral health status of populations worldwide. The Decade of Action for Healthy Teeth and Mouths (2008-2018) set ambitious targets to reduce the prevalence of oral diseases. One of the key targets was to reduce the Decayed, Missing, and Filled Teeth (DMFT) index in 12-year-old children.

**Why the Correct Answer is Right**
The correct answer, **<3 DMFT at 12 years**, is based on the WHO's target to reduce the DMFT index to less than 3 in 12-year-old children by the year 2000. The DMFT index is a widely used measure of oral health, which takes into account the number of decayed (D), missing (M), and filled (F) teeth in individuals. A lower DMFT index indicates better oral health. The WHO's target of <3 DMFT at 12 years reflects the organization's goal to reduce the burden of oral diseases and promote good oral health habits.

**Why Each Wrong Option is Incorrect**
**Option A:** <2 DMFT at 12 years is too stringent and not a realistic target for many countries, especially those with limited resources.
**Option C:** <4 DMFT at 12 years is higher than the intended target and would not effectively reduce the burden of oral diseases.
**Option D:** <5 DMFT at 12 years is even higher and would not align with the WHO's goal of improving oral health.

**Clinical Pearl / High-Yield Fact**
The DMFT index is a useful measure of oral health, but it has some limitations, such as not accounting for other oral health outcomes like periodontal disease. It's essential to consider other oral health indicators when assessing the oral health status of populations.

**✓ Correct Answer: B. <3 DMFT at 12 years**