The answer is B. A good way determine this is how far right the element is on the periodic table. The further right the element is, the more electronegative it is meaning it is more willing to accept an electron. This can be explained using the valence electrons and how many need to be added or removed to complete the octet. The further right you are, the easier it is for the element to just gain a few electrons instead of loose a bunch. Noble gases are the exception to this since they don't normally react though.
I think that the answer is a size and speed
The boiling points of alkanes increases with increasing number of carbons. This is because the intermolecular attractive forces, although individually weak, become cumulatively more significant as the number of atoms and electrons in the molecule increases.
So therefore your answer choice will increase. (B)
