Final answer:
When sound is closer to one ear, it must travel a shorter distance to arrive at the far ear, resulting in an increase in intensity and loudness.
Step-by-step explanation:
The correct answer is d) closer, longer, increase.
When sound is closer to one ear, it must travel a shorter distance to arrive at the far ear. As a result, the distance the sound wave travels increases. This leads to an increase in the intensity of the sound wave, causing an increase in loudness.
For example, if you are standing near a loudspeaker at a concert, the sound waves will travel a shorter distance to reach your ear, resulting in a higher intensity and louder sound.