**Core Concept**
The case describes a newborn with symptoms suggestive of a condition affecting the upper gastrointestinal tract, leading to polyhydramnios in the antenatal period. This indicates a possible esophageal obstruction or disorder.

**Why the Correct Answer is Right**
The symptoms of frothing, excessive drooling of saliva, and coughing of saliva are characteristic of esophageal atresia, a congenital anomaly where the esophagus does not develop properly. Polyhydramnios occurs due to the inability of the fetus to swallow amniotic fluid, leading to an excessive accumulation. Difficulty in passing a nasogastric tube further supports the diagnosis, as the tube cannot be advanced beyond a certain point due to the obstruction.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the clinical presentation of the newborn, which suggests an esophageal issue rather than a cardiac or respiratory problem.
* **Option B:** Although pyloric stenosis can cause projectile vomiting, it typically presents later in infancy and does not explain the polyhydramnios or difficulty passing a nasogastric tube.
* **Option C:** Tracheoesophageal fistula can cause aspiration of saliva and feeds, but it typically presents with symptoms of feeding difficulties and aspiration pneumonia, rather than the specific combination of symptoms described.
* **Option D:** This option is not a recognized clinical diagnosis and does not explain the symptoms or polyhydramnios.

**Clinical Pearl / High-Yield Fact**
In cases of suspected esophageal atresia, it is essential to perform a chest X-ray to confirm the diagnosis and rule out other anomalies. A classic sign is the "coiled spring" appearance of the distal esophagus due to the presence of a pouch.

**Correct Answer:** C. Tracheoesophageal fistula.