Final answer:
Paul has been in the war for approximately one month.
Step-by-step explanation:
In order to determine how long Paul has been in the war, we need to examine the options provided. The correct answer is a) Almost one month.
This can be inferred from the soldier's statement that he was there a month ago. Since Paul is still present, it indicates that he has been there for almost one month.
Therefore, Paul has been in the war for approximately one month.