Answer:
-3.396 m/s or 3.465 m/s
Explanation:
v = Speed of sound in air = 343 m/s
= Relative speed of the singer
f = Observed frequency
f' = Actual frequency
1% change can mean 
From the Doppler effect equation we have

The velocity is -3.396 m/s
when 

The velocity is 3.465 m/s
Frequency= speed/ wavelength
=0.5m/s divided 0.1.m
=5.0 Hz
The answer would be letter D.
the element has 7 valance electrons is CI:Chlorine
<em>"A concave lens is thinner at the center than it is at the edges."</em>
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