**Core Concept**
The International Classification of Diseases (ICD) is a comprehensive system for categorizing diseases and health-related conditions, developed by the World Health Organization (WHO). The ICD-11 is the latest revision, which includes changes to terminology used in psychiatric conditions. The concept of intellectual disability or mental retardation has been revised to better reflect current understanding and use of more person-centered language.

**Why the Correct Answer is Right**
The term "Disorders of intellectual development" is used in the ICD-11 to describe a condition characterized by significant limitations in both intellectual functioning (such as learning, reasoning, problem-solving) and in adaptive behaviors, which cover a range of everyday social and practical skills. This term acknowledges that intellectual disability is a lifelong condition that affects an individual's development and functioning. The use of "disorders" instead of "retardation" is a deliberate choice to focus on the condition as a medical disorder rather than a personal failing.

**Why Each Wrong Option is Incorrect**
**Option A:** "Intellectual disability" is an older term that is still widely used, but it has been replaced by "Disorders of intellectual development" in the ICD-11 to better reflect current understanding and language use.
**Option C:** "Mental instability" is a term that refers to a state of being unstable or unpredictable, often used to describe individuals with mood disorders or personality disorders, but it is not a specific diagnosis for intellectual disability.
**Option D:** "Intellectual deterioration" is a term that implies a decline in intellectual functioning over time, which may be seen in certain neurodegenerative conditions, but it is not a specific diagnosis for intellectual disability.

**Clinical Pearl / High-Yield Fact**
When communicating with patients or families about a diagnosis of intellectual disability, it is essential to use person-centered language and focus on the individual's strengths and abilities rather than their limitations. Using the term "Disorders of intellectual development" can help to promote a more positive and empowering approach to care.

**✓ Correct Answer: B. Disorders of intellectual development**