Rin heard nothing intelligible , as if words had already fled far beyond his reach . He let out a slight grunt , then a louder one . His attention turned inward ; his eye dilated and his brow creased . Thrusting his hand further under his clothing , he seemed to search around in the area of his groin - surely he had n't lost track of that ?
According to the above context, choose the best option to answer the following question.
Question: What may be the reason he let out a loud grunt .
Options:
- None of the above choices .
 - He was transforming from a man into a pig .
 - He wanted to scare any children out nearby .
 - He was in a tremendous amount of pain .


He was in a tremendous amount of pain .