By retaining which substance can marine fishes keep their body fluids hypertonic to the surrounding seawater?

1. A Option A: Trimethylamine oxide
2. B Option B: Excess urea, which raises their internal solute concentration and prevents shrinkage in a hypertonic environment
3. C Option C: Trimethyl alanine
4. D Option D: Ammonia

Answer checked 11 October 2026 · How we write and check questions