(a) The smallest SD is 0, when all the numbers are the same (since repeats are allowed). There is no deviation from the mean.
(b) The largest SD is when the numbers are 0, 0, 10, 10. The mean is 5 and the variance is 4×25/4=25. The SD is 5.
(c) There are 11 possible datasets for (a), since there are 11 whole numbers between 0 and 10. For (b) there is only one dataset.