## **Core Concept**
H. influenzae type b (Hib) meningitis is a serious infection that can lead to significant morbidity and mortality in children. One of the complications of Hib meningitis is the development of **asymptomatic inner ear effusion** or **otitis media with effusion (OME)**, which can cause hearing loss.

## **Why the Correct Answer is Right**
The correct answer, **Audiometry**, is essential because children with H. influenzae meningitis are at risk of developing hearing loss due to the spread of infection to the inner ear or due to the inflammatory response. Early detection of hearing loss through **audiometry** allows for timely intervention, such as hearing aids or speech therapy, which can significantly improve outcomes.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is blank and does not provide a viable alternative for consideration.
- **Option B:** This option is also blank and does not offer a reasonable investigation.
- **Option C:** Similarly, this option is blank and lacks relevance to the required investigation.
- **Option D:** This option is blank as well.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that **all children with bacterial meningitis, including those caused by H. influenzae, should undergo audiologic evaluation before hospital discharge** to detect potential hearing loss early. This is crucial because some cases of hearing loss may be **asymptomatic** and can significantly impact a child's development if not addressed promptly.

## **Correct Answer:** D. Audiometry.