A low-pass filter with a cut-off frequency of 30HZ is cascaded with a high-pass filter with a cut-off frequency of 20HZ. The resultant system of filters will function as

A low-pass filter with a cut-off frequency of 30HZ is cascaded with a high-pass filter with a cut-off frequency of 20HZ. The resultant system of filters will function as   (GATE-EE-2011)

A. an all-pass filter
B. an all-stop filter
C. a band stop (band reject) filter
D. a band-pass filter 

Explanatory answer :

Low-pass filter with a cut-off frequency of 30HZ:

High-pass filter with a cut-off frequency of 20HZ:

The cascade combination filter is

A band-pass filter