This is just a guess based on some quick background research I just did. I think "Bookmarking a Blog" would be the worst way to keep up with the latest blog posts.
Bookmarking a Blog: I don't think that bookmarking a blog website would send you update notifications. Therefore, I think this answer choice would be the least productive way to keep up with latest blog posts.
RSS feed subscription: RSS stands for "Really Simple Syndication" it is an easy way to distribute update notices and headlines to a large group of people. (This sounds like a good way to keep up with a blog.)
Visiting the blog every few days: This sounds tedious, but if you have the time for it I suppose this would be a good way to make sure your not missing any blog posts.
Adding the blog to an online reader: I am not quite sure what they mean by this answer choice. I am guessing that they mean adding it to a online reading list? If so, then you would be notified of any new blog posts from your blogs added to your reading list.
I hope that all made sense and that I am right in my answer! Please, let me know if I made a mistake or if I gave you the wrong answer. I would like to improve for similar questions in the future.
You can see the tools next to the person which usually means work. This can refer to how they worked to get money where the money is on the opposing side of the person.
