**Core Concept**
Audiometric evaluation in infants requires a non-invasive, objective, and reliable method to assess hearing sensitivity. The chosen investigation should be capable of detecting even slight deviations in hearing thresholds, as early detection and intervention are crucial for optimal language development.

**Why the Correct Answer is Right**
Otoacoustic Emissions (OAE) testing is the preferred method for audiometric evaluation in infants. This technique measures the sound generated by the cochlea's outer hair cells in response to external auditory stimuli. OAE testing is based on the principle that a normally functioning cochlea will generate a specific sound pressure level in response to a stimulus, which can be detected by a sensitive microphone. This method is particularly useful in infants because it is non-invasive, quick, and does not require active participation from the child.

**Why Each Wrong Option is Incorrect**
**Option A:** Behavioral audiometry, such as visual reinforcement audiometry (VRA) or conditioned play audiometry (CPA), is used in older children and adults to assess hearing thresholds. However, these methods require active participation from the child and may not be suitable for infants.
**Option B:** Pure-tone audiometry is a common method for assessing hearing thresholds in adults and older children. However, it relies on the patient's ability to respond to sounds, which is not feasible in infants.
**Option C:** Acoustic immittance testing, including tympanometry and acoustic reflex measurement, is used to assess middle ear function. While it can provide valuable information about middle ear status, it is not a direct measure of hearing sensitivity.

**Clinical Pearl / High-Yield Fact**
Early detection of hearing loss in infants is critical for optimal language development. The American Academy of Pediatrics recommends that all newborns undergo hearing screening before discharge from the hospital, and that infants who fail screening should undergo further evaluation, including OAE testing.

**Correct Answer: D. Otoacoustic Emissions (OAE) testing**