We've got to do some calculations, right? I mean, if you can't figure out how to do it without calculations, maybe we had better calculate? Average is not too hard. Sum of negatives is -23, positives is 48....average is thus 25/6=4 and 1/6.
Standard deviation, as I understand it, is average distance from mean to any given number in the set. Keeping 25/6 in mind and looking through the set of numbers, it becomes clear in a hurry that the standard deviation is going to be quite a lot more than the mean. For every single number in the set, its distance to the mean exceeds the mean itself. A little under 8 to get from mean to 12, a little over 6 to get to -2 (from the mean)....and it just goes up from there.
As for median, numbers are in order, middle two are -2 and 12, add 'em up, divide by 2. 10/2=5
ii) and iii) look false.
i) looks true.