Which one of the following is not included in the S-block?

Which one of the following is not included in the S-block?

مندرجہ ذیل میں سے کون سا ایس بلاک میں شامل نہیں ہے؟
Explanation

Fe (Iron) belongs to the d-block.

While Na, Mg, and K are elements of the S-block in the periodic table.