A part of the periodic table is shown. A portion of the sixteenth and seventeenth columns of the periodic table is shown. Column 16 reads eight oxygen, 16 sulfur, and 34 selenium. Column 17 reads nine flourine, 17 chlorine, and 35 bromine. (there is also a pic)

Which of the following elements is less reactive than the others?

Bromine (Br)
Oxygen (O)
Selenium (Se)
Sulfur (S)

Thanks again and I hope to see everyone again and again I apologise I didn't know you had mentioned

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

if it's not useful, feel free to report for mistake in answer.