$$(√2-√3)^2$$ is :

Correct option is C

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Given:

Expression:
​$$(\sqrt{2} - \sqrt{3})^2$$​​

Solution:

We use the identity $$(a - b)^2 = a^2 - 2ab + b^2$$​​

​$$(\sqrt{2} - \sqrt{3})^2 = (\sqrt{2})^2 - 2 \cdot \sqrt{2} \cdot \sqrt{3} + (\sqrt{3})^2\\\ 2 - 2\sqrt{6} + 3\\= 5 - 2\sqrt{6}$$​​

Since $$5 - 2\sqrt{6}$$​ includes the irrational term $$\sqrt{6},$$​ it is an irrational number.

Thus, the correct answer is **Option C: An irrational number**.