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**Hint:**In physics, the sensation of frequency of the sound waves is commonly known as pitch of the sound and it’s directly proportional to the frequency of sound waves. A higher frequency sound will have more pitch than the wave having low frequency.

**Complete step by step answer:**

Let us examine the apparent frequency for stationary observers and will determine the pitch.Suppose the original frequency of the siren of police car is denoted by $\nu $ and the apparent frequency for the observer when police car is moving away from the observer denoted as $\nu '$ which is given as:

$\nu ' = \nu (\dfrac{{{V_{sound}}}}{{{V_{sound}} + {V_{source}}}})$

Where, ${V_{sound}}$ Is the speed of sound in air and ${V_{source}}$ is the speed of the source which is the police car in the given question.

Now, calculating the apparent frequency when source moves towards the stationary observer:

$\nu '' = \nu (\dfrac{{{V_{sound}}}}{{{V_{sound}} - {V_{source}}}})$

Now, we can see that Denominator in second case is less than in first case, which shows

$\nu '' > \nu '$

So, the frequency of the siren approaching the stationary observer is greater than the frequency of moving away from the siren.

**Hence, the correct option is A.**

**Note:**It should be remembered that pitch is just a representation of how high or low the frequency of sound wave is and frequency of sound wave for a relative observer is also affected by speed of wind when this speed of wind is comparative to the speed of source and speed of sound waves.

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