which of the following statement about the normal distribution is TRUE?

a) The area under the curve from one standard deviation above the mean to infinity is equal to 50% of the probability distribution.

b) About 2/3 of the observatiions falls within -1 and +1 standard deviation from the mean.

c) The normal curve is symmetrical around its standard deviation.

d) The mean and median must be the same but the mode may be different value.