**Core Concept**
Kanagawa's phenomenon is a hemolytic activity observed on Wagatsuma agar at 37°C, which is characteristic of Vibrio parahemolyticus. This phenomenon is used to differentiate V. parahemolyticus from other Vibrio species.

**Why the Correct Answer is Right**
Vibrio parahemolyticus is a halophilic, Gram-negative bacterium that causes gastrointestinal illness. The Kanagawa phenomenon is due to the production of two hemolysins, TDH (Thermostable Direct Hemolysin) and TDH-R (Thermostable Direct Hemolysin-related hemolysin). These hemolysins are responsible for the hemolytic activity observed on Wagatsuma agar at 37°C. The production of these hemolysins is a key virulence factor for V. parahemolyticus.

**Why Each Wrong Option is Incorrect**
**Option A:** Pseudomonas aeruginosa is a Gram-negative bacterium that can cause a variety of infections, but it does not exhibit the Kanagawa phenomenon.
**Option C:** Shigella sonnei is a Gram-negative bacterium that causes dysentery, but it is not associated with the Kanagawa phenomenon.
**Option D:** Proteus mirabilis is a Gram-negative bacterium that can cause urinary tract infections, but it does not exhibit the Kanagawa phenomenon.

**Clinical Pearl / High-Yield Fact**
The Kanagawa phenomenon is a key diagnostic feature of Vibrio parahemolyticus, which is a major cause of seafood-borne gastroenteritis. This phenomenon is used to differentiate V. parahemolyticus from other Vibrio species and is an important tool in the diagnosis of gastrointestinal illness.

**✓ Correct Answer: B. Vibrio parahemolyticus**