Why are quartiles generally more reliable for judging outliers than mean and standard deviation?

Quartiles are generally more reliable for judging outliers than mean and standard deviations for 2 reasons. The mean is simply the average of all of the numbers, meaning that an outlier can easily be obscured by the masses. Standard deviation is a better method, however only going over by one standard deviation in either direction would also mask an outlier. A strong outlier however will pull a quartile farther in that direction than would normally be expected.

None of the options you showed are it.