Final answer:
According to the decibel scale, a sound of 90 decibels (dB) is 10 times more powerful than a sound of 0 decibels (dB).
Step-by-step explanation:
The decibel (dB) scale is a logarithmic scale used to measure the intensity of sound. According to the scale, a sound of 90 decibels (dB) is 10 times more powerful than a sound of 0 decibels (dB). This is because each increase of 10 decibels represents a tenfold increase in sound intensity. Therefore, the correct answer is b) 10 to the power of 9.