**Core Concept**
The standard normal distribution, also known as the z-distribution, is a probability distribution of a continuous random variable with a mean of 0 and a standard deviation of 1. The area under the standard normal distribution curve represents the probability of a value falling within a given range.

**Why the Correct Answer is Right**
The area under the standard normal distribution curve is equal to 1, representing the total probability of all possible values. This is because the curve is a continuous probability distribution, and the sum of all probabilities equals 1. The standard normal distribution is symmetric around the mean (0), and the area under the curve is equally divided on both sides of the mean.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the area under the normal distribution curve does not depend on the mean or standard deviation of the distribution. However, the area under the curve is always equal to 1, regardless of the distribution's parameters.

**Why Each Wrong Option is Incorrect (continued)**
**Option B:** This option is incorrect because the area under the curve is not dependent on the specific value of the mean. While the mean is a key parameter of the normal distribution, the area under the curve remains constant at 1.

**Why Each Wrong Option is Incorrect (continued)**
**Option D:** This option is incorrect because the area under the curve does not decrease as the standard deviation increases. In fact, the area under the curve remains constant at 1, regardless of the standard deviation.

**Clinical Pearl / High-Yield Fact**
Remember that the area under the standard normal distribution curve represents the total probability of all possible values, and it is equal to 1. This is a fundamental concept in statistics and probability theory.

**Correct Answer:** C. 1