**Core Concept**
The intensity of sound reaching the ear is measured in decibels (dB). In a normal conversation, the intensity of the voice is around 60 dB, which is within the safe range for human hearing. This is because the sound intensity decreases with distance according to the inverse square law.

**Why the Correct Answer is Right**
The correct answer is based on the inverse square law, which states that the intensity of a sound decreases with the square of the distance from the source. In this case, the sound intensity at 1 meter is 60 dB. This value is within the normal range for human conversation and is not loud enough to cause hearing damage. The ear's sensitivity to sound is also an important factor in determining the perceived intensity.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided, so we cannot evaluate it.
* **Option B:** This option is not provided, so we cannot evaluate it.
* **Option C:** This option is not provided, so we cannot evaluate it.
* **Option D:** This option is not provided, so we cannot evaluate it.

**Clinical Pearl / High-Yield Fact**
The intensity of sound above 85 dB can cause hearing damage, while sounds above 120 dB can cause immediate harm. It's essential to be aware of the safe sound levels when working with loud machinery or listening to music.

**Correct Answer: C. 60 dB.**