Air pollution causes ALL of the following EXCEPT: QU
unhealthy air to breath
U
smog
decreased particles in the air
holes in the ozone layer
d

The frequency of a certain wave is the quotient obtained by dividing the speed of the wave by the wavelength. That is 
                                          f = s/λ
Substituting the known values,
                                          f = (5.6 m/s) / 3.3 m
                                             = 1.7/s
                                             = 1.7 Hz