Step 1: Disproportionation of \( \text{XeF}_4 \).
When xenon tetrafluoride (\( \text{XeF}_4 \)) is disproportionated in water, it gives xenon tetroxide (\( \text{XeO}_4 \)) and hydrofluoric acid (HF) as products. This is a typical disproportionation reaction of xenon compounds.
Step 2: Conclusion.
The correct answer is (C), \( \text{XeO}_4 \) and HF.