8. (15 points) A and B are playing a game of writing numbers on the blackboard: each time they write a number, it must be a positive integer not exceeding 10, and no repetition is allowed; starting from the third number, each number must also be the difference of two previously written numbers. The player who cannot write a number loses the game. Question: If A starts first, who has a sure-win strategy?
8. Player B has a winning strategy.

Consider the first number written by Player A.
If Player A writes an even number, Player B writes half of this number, then Player A cannot write again.
If Player A writes an odd number:
(1) If Player A writes 1, then Player B writes 2; if Player A writes 3, then Player B writes 6; if Player A writes 5, then Player B writes 10. In all three cases, Player A cannot write again, and Player B wins.
(2) If Player A writes 7 first, then Player B writes 8, denoted as $(7,8)$, the next number written is $(1,6)$, followed by $(2,5)$, $(3,4)$, and finally, it must be Player A's turn to be unable to write.
(3) If Player A writes 9, then Player B writes 10, denoted as $(9,10)$. The next numbers can be divided into 4 groups: $(1,8)$, $(2,7)$, $(3,6)$, $(4,5)$. Each time Player A writes the first number in a group, Player B writes the second number in that group, and eventually, it must be Player A's turn to be unable to write (the numbers in the group with a border indicate that the two numbers can be swapped).
(Zhang Tongjun provided)