Four separate areas of study make up a full CompTIA A+; you're qualified as an A+ achiever when you've achieved certifications for 2 out of 4 subjects. For this reason, it's usual for colleges to only have two of the courses on their syllabus. In reality you're advised to have the training for all four areas as industry will ask for an understanding of all four areas. Don't feel pressured to qualify in them all, although it would seem prudent that you take tutorials in all 4 subjects.