Chebyshev empirical rule

Can you please tell me the correct answer to this question?
The Chebyshev empirical rule used for a normal variable, says that :
a) Approximately 90% of the values in the interval x+3s
b) Approximately 5% of the values are in the ... Interval
c) Approximately 95% of the z-values are in the Interval -2 and 2
d) Approximately 68% of the values are outside the interval -3 and 3