The correct answer is (a) 31.
The mode is the value that occurs most frequently in a data set. The median is the middle value in a data set when the data is arranged in order from least to greatest. The arithmetic mean is the sum of the values in a data set divided by the number of values in the data set.
In this case, the mode is 28 and the median is 31. This means that the value 28 occurs more frequently than any other value in the data set, and that half of the values in the data set are less than or equal to 31, and half of the values in the data set are greater than or equal to 31.
The arithmetic mean is likely to be close to the mode and the median, since these are both measures of central tendency. Therefore, the probable value of the arithmetic mean is 31.
Option (b), 36, is not a probable value of the arithmetic mean, since it is not close to the mode or the median. Option (c), 30, is also not a probable value of the arithmetic mean, since it is less than the median. Option (d), 58, is not a probable value of the arithmetic mean, since it is much greater than the mode and the median.