9. (10 points) The figure below is a floor plan of Xiaoma's new home. The new home has 6 rooms, and the rooms are connected by doors. Xiaoma wants to start from a certain room and walk through all the doors without repeating any, ending at room $F$. Therefore, the room he should start from is ( ) room.
A. $A$
B. $B$
C. $C$
D. $D$
【Answer】Solution: According to the problem, we have:
Convert the figure into a point-line graph:
The number of odd points is 2, which are $A$ and $F$. Therefore, one is the endpoint, and the other is the starting point of the one-stroke drawing problem, with an odd point as the starting point and another odd point as the endpoint. So the starting point is $A$.

Therefore, the answer is: $A$.