dunkin77 wrote:Hi,

I think to meet the condition, x must be positive, but why 2) meet the condition?? the answer is B but could not figure out,..

sqrt [ (x-3)^2 ] will yield a positive answer. Now, depending on the
sign of x, it will be either x-3 or 3-x.

1 - insufficient. x can be > 3 or < 3. So, we don't know if it will be
equal to 3-x

2 - sufficient. -x|x| will be positive when x is negative. Since x is
negative, the final answer will be 3-x and hence sufficient.