The answer would be: K
Kalium or Potassium is one of the metal that located in the first column of the periodic table. It was a strong base with one valence. If react with water it would have an equation:
2K + 2H2O = 2KOH + H2
The kalium hydroxide will form ion if put on the aqueous state. It will become K+ and OH-, thus increasing the water pH.