The intensity of the sound will be B. Nine times lower
Explanation:
The intensity of a sound follows an inverse square law, which means that it is inversely proportional to the square of the distance from the source:

where
I is the intensity
r is the distance from the source
In this problem, the siund has an intensity of I when the receiver is placed at a distance r from the source.
Later, the receiver is placed three times farther away, so the new distance is
r' = 3r
Therefore, the new intensity of the sound will be:

Therefore, the intensity of the sound received will be nine times lower.
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