Hi

If x > 0 the equation is x² + a x + 1 = 0

If x < 0 the equation is x² - a x + 1 = 0

In both cases if -2 < a < 0 there are no roots because the discriminant is < 0

If a < -2 then the discriminant is > 0, you can show that there are 2 real roots which are both > 0 (in the case where x > 0) or both < 0 (in the case where x < 0). There are therefore 4 real roots.

The answer is b