The transfer function of a real system, $H(s)$, is given as:

$H\left ( s \right ) = \dfrac{As + B}{S^{2} + Cs + D}$

where $\text{A, B, C}$ and $D$ are positive constants. This system cannot operate as

1. low pass filter.
2. high pass filter.
3. band pass filter.
4. an integrator.