As I was reading about introverts and extroverts, one thing I found was that introverts do not necessarily dislike public speaking. Many introverts are great public speakers and have no problem giving speeches that they've had time to prepare. However, the thought of approaching 100 people to knock on their door is generally very distasteful to most introverts. Therefore, someone who would rather give the speech than knock on the doors is likely to be an introvert.
On the second question, writing a letter is something that can best be done in private. Again, an introvert would generally prefer that kind of private action rather than being in public with a group of people and being seen by others.
The third question is more of the same. Generally, an introvert doesn't like being drawn into something on the spur of the moment. Instead, an introvert will be more comfortable with the option of being able to give responses careful thought as people can do on a message board.
If you really don't have a preference in any of those scenarios, you are likely equally balanced between being an introvert and an extrovert. An important point is to be able to separate what you really find most appealing from what you believe you have to do because of your religious beliefs. I'm not saying that there's anything wrong with going outside your comfort zone for a calling, but in the long run, you're probably better off knowing who you really are to know whether what you see as a calling is really outside your zone.
Bill
Thanks, Bill, no, seriously; I really DO enjoy all those activities.
I do especially like (Door-to-Door) though!