The correct answer is b) 6.
Selenium (Se) is located in group 16 of the periodic table, which is also known as the chalcogen group. Elements in this group typically have six valence electrons. This is because the valence electrons are the electrons located in the outermost shell of an atom, and these are the electrons involved in chemical bonding.
To visualize this, selenium has an atomic number of 34, which means it has 34 electrons. The electron configuration for selenium is [Ar] 4s² 3d¹⁰ 4p⁴, indicating that there are a total of six electrons in the outermost shell (4 from the 4s orbital and 4 from the 4p orbital). Therefore, when considering how many valence electrons selenium has, the number is six.