1. There are 1000 numbers arranged in a row, where among any three consecutive numbers, the middle number equals the sum of the numbers before and after it. If the first number and the second number are both 1, then the sum of these 1000 numbers is
A. 1000
B. 1
C. 0
D. -1
1. B According to the problem, the 1000 numbers are arranged as follows: $1,1,0,-1,-1,0,1,1,0,-1,-1,0, \cdots$ In other words, they cycle in a pattern of $1,1,0,-1,-1,0$.
Since $1000 \div 6=166 \cdots \cdots 4$, and the sum of the 6 numbers in each cycle is 0, the sum of these 1000 numbers is $1+1+0+(-1)=$ 1. Therefore, the answer is B.