The answer is B. In order to hit an application without hitting the web server, you would use the default host port on the application server. If this sounds confusing to you, let me break it down into simpler terms. Let us say that you received a new message on Facebook on your phone.
Instead of using the web browser to go to the Facebook website to open this message, you would simply use the Facebook application to avoid using the web server. If you have access to or own a telephone, chances are that you have performed this task several times even if you did not realize that is what you were doing.
The best answer to this is B. If you do not understand how this occurs, just imagine if you are going to need to open something from your email on your phone. If you already have the application installed on your phone, then you do not need to go through the web server anymore.
This can be convenient for a lot of people because normally, applications can work faster as compared to web servers. If you do not have the applications installed on your phone, then the process would still require going through the website. It will depend on you if you still want this or not.