The mean and standard deviation of the scores are 75 and 9.5 respectively.
The z-score is a means to find the probability of getting a particular score. This is calculated to be:

where x is the score, μ is the mean, and σ is the standard deviation.
To be a part of the top 2.5 percent, the probability is:

The z-score for this probability, that is, P
0.9 seconds is the correct answer
Graph D, because no x-value repeats and it passes the vertical line test.