Q. 10 The impulse response h(t) of a linear time invariant continuous time system is described by 
where u(- t) denotes the unit step function, and a and b are real constants. This system is stable if
(A) a is positive and b is positive
(B) a is negative and b is negative
(C) a is negative and b is negative
(D) a is negative and b is positive
Answer: D
Explanation:
