**Core Concept**
The World Health Organization (WHO) has established a case definition for AIDS that includes major and minor signs, focusing on symptoms that are indicative of severe immunosuppression. These signs are critical for the clinical diagnosis of AIDS, especially in resource-limited settings. The **immune system suppression** leads to various opportunistic infections and conditions.

**Why the Correct Answer is Right**
The correct answer includes a combination of symptoms that are characteristic of advanced HIV infection or AIDS, such as **prolonged fever**, **chronic diarrhoea**, and **weight loss**, which are all indicative of severe immunocompromise. These symptoms can result from opportunistic infections or malignancies that take advantage of the weakened immune system. The **WHO case definition** aims to standardize the diagnosis based on clinical presentation.

**Why Each Wrong Option is Incorrect**
**Option A:** Generalized lymphadenopathy can be an early sign of HIV infection but is not specific to AIDS.
**Option C:** While cough can be a symptom of various opportunistic infections, a prolonged cough alone is not a defining criterion for AIDS without specifying an underlying cause like tuberculosis.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the diagnosis of AIDS often relies on a combination of clinical symptoms and laboratory confirmation of HIV infection, especially in settings with access to such testing. The presence of **opportunistic infections** or **cancers** is highly suggestive of AIDS.

**Correct Answer:** D. b, d, e. Prolong fever more than 1 month, Chronic diarrhoea > 1 month, Weight loss > 10%