The correct options are
C Magnesium reacts with steam.
D Potassium reacts with cold water.
∙ Potassium reacts vigorously with cold water to form potassium hydroxide and hydrogen gas. This can be represented as:
Potassium+Water→Potassium hydroxide+Hydrogen gas
∙ Magnesium is less reactive in nature. It does not react with cold water. It reacts with steam to form magnesium hydroxide and hydrogen gas. The reaction involved is:
Magnesium+Water→Magnesium hydroxide+Hydrogen gas
∙ All metals do not react with water. For example: noble metals (gold, silver, platinum).