Here you go I just googled it
Answer:
it readily gains another electron. the outer electron shell is closer to the nucleus, than iodine for example, which makes it less shielded (greater attraction for another electron = violent reaction to get it)
Explanation:
Those elements with similar properties are in the same column.
I would say B because c and d would decrease competition and a would do the same, or just kill the ecosystem.
Hope this helps and don't forget to hit that heart :)
Atoms in covalent bonds do combine so as to be stable. As covalent bond consist non metals e.g O2 in this example each atom has vacance of 2 orbitals/ electrons so shairing electrons result their stability
