X is the base which is soluble in water. Then the metal present in the base is(1) aluminium (2) sodium (3) copper (4) iron

To determine which metal present in the base $X$ is soluble in water, we need to evaluate the solubility of bases formed by the metals listed:

1. Aluminium: Aluminium hydroxide $\text{Al(OH)}_3$ is not soluble in water, but sodium aluminate can dissolve in water under certain conditions.

2. Sodium: Sodium hydroxide $\text{NaOH}$ is highly soluble in water, forming a strong alkaline solution.

3. Copper: Copper hydroxide $\text{Cu(OH)}_2$ is poorly soluble in water.

4. Iron: Iron hydroxide $\text{Fe(OH)}_3$ is not soluble in water.

Conclusion:

Among the options provided, sodium (option 2) is the metal present in the base that is soluble in water. Thus, the answer is sodium.