The z-score of a measure is given by the following formula

where x represents the measure, mu represents the mean of the distribution, and sigma represents the standard deviation.
If we have a z-score equal to zero, our measure will be

a z-score equal to zero represents the mean of the distribution.
For a z-score equal to 1, we have

Then, the interval between z = 0 and z = 1 is the interval between the mean and one positive standard deviation.

The graph that represents this interval is the first graph.