Let’s fill in the blank with all the possible options.
Some people argue, CONSEQUENTLY, that because he has natural advantages over other swimmers, it was not fair that he won eight gold medals in 2008.
Some people argue, FIRST OF ALL, that because he has natural advantages over other swimmers, it was not fair that he won eight gold medals in 2008.
Some people argue, FOR THE SAME REASON, that because he has natural advantages over other swimmers, it was not fair that he won eight gold medals in 2008.
Some people argue, EQUALLY IMPORTANT, that because he has natural advantages over other swimmers, it was not fair that he won eight gold medals in 2008.
We can eliminate the last two options because they don’t use correct grammar. The first two are possible options, but one is more plausible than the other. Consequently makes the most sense because the people argue as a CONSEQUENCE of the swimmer having natural advantages that allow him to win several gold medals.
