For a standard normal probability distribution, the mean (μ) and the standard deviation (s) are :

The simplest case of a normal distribution is known as the standard normal distribution. This is a special case when μ = 0 and σ = 1, and it is described by this probability density function:

Here, the factor  ensures that the total area under the curve ϕ(x) is equal to one. The factor 1/2 in the exponent ensures that the distribution has unit variance (i.e., variance being equal to one), and therefore also unit standard deviation. This function is symmetric around x = 0, where it attains its maximum value  and has inflection points at x = +1 and x = -1.

Thus, option 1 is the correct answer.