Answer the following question given this paragraph: 

Potassium is a soft, silvery metal that ignites explosively in water. It easily loses its one valence electron to form positive potassium ions (K + ), which are needed by all living cells. Potassium is so important for plants that it is found in almost all fertilizers, like the one shown here. Potassium is abundant in Earth’s crust in minerals such as feldspar.


Q: Potassium is a soft, silvery metal that ignites explosively in what?


A:
water