Official solution
Note that (a, b) and (b, c) satisfy 0 < |x - y| \[\le\] 1 but (a, c) does not satisfy it so 0 \[\le\] |x - y| \[\le\] 1 is symmetric but not transitive.
For example,
x = 0.2, y = 0.9, z = 1.5
0 \le |x -- y| = 0.7 \le 1
0 \le |y -- z| = 0.6 \le 1
But |x -- z| = 1.3 > 1
So, (b) is correct.