**Core Concept**
The question is testing the clinical diagnosis of a child presenting with specific facial abnormalities and symptoms, which are characteristic of a congenital condition affecting the development of the jaw and surrounding structures.

**Why the Correct Answer is Right**
The most probable diagnosis in this case is Pierre Robin Sequence (PRS), a condition characterized by micrognathia (small lower jaw), retrognathia (retracted lower jaw), and glossoptosis (tongue displacement into the pharynx). This condition often results from a failure of the tongue to descend from the pharynx during fetal development, leading to an abnormal formation of the jaw and surrounding tissues.

**Why Each Wrong Option is Incorrect**
* **Option A:** Cleft palate, while a possible congenital anomaly, does not typically present with micrognathia and retrognathia.
* **Option B:** Trisomy 21 (Down syndrome) may present with various facial abnormalities, but it is not the most probable diagnosis given the specific combination of symptoms in this case.
* **Option C:** Crouzon syndrome is a genetic disorder affecting craniofacial development, but it typically presents with other characteristic features such as exophthalmos, flat face, and a short upper jaw.

**Clinical Pearl / High-Yield Fact**
Pierre Robin Sequence is often associated with other congenital anomalies, such as cardiac defects and hearing loss, which may require careful evaluation and management.

**Correct Answer:** D. Pierre Robin Sequence.