imo A - but with substitution
statement 1 says: 1/(k-1)>0
as we know k cannot be 0,1 or -1
with statement 1 it is also true that k cannot be a negative number
for example k = -2
then,
1/(k-1)>0 becomes 1/(-2-1) or 1/(-3)>0 or -1/3>0 (which cannot happen)
so K always has to be positive and if k is positive then 1/(+ve k) is always greater than 0
NOW MOVING ON.....
Statement 2
1/(k+1)>0
if K is positive we are good as 1/(+ve K) will always be greater than 0.
but if K is -0.5
then 1/(-0.5+1)>0
or 1/0.5 > 0
or 2>0
statement 2 holds true but it makes 1/k = 1/(-0.5) = -2 which is less than 0
so statement 2 is insufficient
Remember: If the question does not mention the word integer, test for fractions as well.