Perhaps the worst group of the tournament, Argentina lucked out here. Look for the South Americans to run away with this group and clean sweep it. I see the Bosnians coming in second, followed by Nigeria and Iran. Iran will struggle to register a point at the tournament, though just reaching the tournament is an accomplishment.
Argentina - The front runners of the group by far, Lionel Messi will look to end his World Cup scoreless streak and find the back of the net multiple times. He will have help in Sergio Kun Aguero and Angel di Maria, who will help the Argentines fly into the knockout stage and maybe even beyond that. They know the South American climate better then most teams, and can use this greatly to their advantage.
Bosnia & Herzegovina - Bosnia will be able to finish second in the group, behind Argentina. They have a good forward line, led by Edin Dzeko, of Manchester City, and are solid in net with Stoke City keeper Asmir Begovic. I look for them to get out of the group stage and into the knockout round, but advance no further. They will most likely end their tournament in the round of 16, however this is still a huge accomplishment having not even participated in the tournament 4 years ago.
Iran - Not much to say, I don't see them registering a point at the tournament. However, it is still a massive accomplishment for them to be at the tournament. Iran defeated Trinidad and Tobago in their final World Cup tune up game 2-0, which may give the side something to play off of at the World Cup. They're hoping the momentum of this win can carry them through the tournament, and land them at the very minimum a draw. Who knows maybe they will find themselves in the knockout round, it is a weak group and strange things do happen at the FIFA World Cup.
Nigeria - The Nigerian Super Eagles are coming off an underwhelming final warm up game vs. the United States in which they were outplayed and outclassed for 90 minutes. They fell 2-1, getting their goal on a late penalty kick, however they looked poor throughout. Unless things drastically change in not much time I don't see them getting past the group stage of the World Cup.