**Core Concept**
Essential drugs are a list of medicines that are considered necessary for a basic healthcare system. They are selected based on their efficacy, safety, and cost-effectiveness, and are intended to meet the needs of the majority of the population.

**Why the Correct Answer is Right**
The World Health Organization (WHO) defines essential drugs as those that satisfy the health care needs of the majority of the population. These drugs are selected through a rigorous process that considers their therapeutic value, safety, and cost-effectiveness. The WHO Essential Medicines List (EML) is updated periodically to reflect changes in disease patterns, new technologies, and emerging evidence. The EML serves as a guide for countries to develop their own lists of essential medicines.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because essential drugs are not solely determined by their price. While cost-effectiveness is an important consideration, it is not the only factor.
**Option B:** This option is incorrect because essential drugs are not limited to the treatment of acute conditions. They may also include drugs for chronic disease management and preventive care.
**Option C:** This option is incorrect because essential drugs are not necessarily the most expensive or high-tech options available. In fact, many essential drugs are relatively inexpensive and have been available for decades.

**Clinical Pearl / High-Yield Fact**
The WHO Essential Medicines List (EML) is updated every two years, and the current list includes over 450 medicines that are considered essential for a basic healthcare system.

**Correct Answer: D.**