Hey u have fallen for a trap.
you have taken X as only integers in statement 1.

i could take x= -0.5 then (1- x^2) is positive and x^3 is negative.
Thus x^3 (1-x^2) is still < 0

But when x = 3, the statement 1 still hold good.

so we have 2 values of x, one positive and one negative. Thus insufficient.

Statement 2: x^2 <1
so x could again be positive or negative. Insufficient

Combine both, you definitely know that x^2 < 1,
then 1- x^2 is definitely positive. So inorder for the statement 1 to be true, x^3 has to be negative.
Therefore X is negative.
Thus you need both the statements to determine whether x is negative.

Thus the answer is C.

yeah right,i forgot that...thanks