The output y(t) of a continues-time system S for the input x(t) is given by?
$$y\left( t \right) = \int\limits_{ - \infty }^t x \left( \lambda \right)d\lambda $$
Which one of the following is correct?

A. S is linear and time-invariant

B. S is linear and time-varying

C. S is non-linear and time-invariant

D. S is non-linear and time-varying

Answer: Option A