another DS

In such questions always remember mean is the mid point which means 50% values is greater than the mean and 50% are below the mean

Mean = m

SD=d

Always remember the 68-95-99.8 rule of statistics

Here is a link which will help you understand this rule
https://en.wikipedia.org/wiki/68-95-99.7_rule

Mean + 1stSD = m+d - 34%
Mean + 2ndSD = m+2d - 14%
Mean + 3rdSD = m+3d - 2%

similarly for below the mean

Mean - 1stSD = m-d - 34%
Mean - 2ndSD = m-2d - 14%
Mean - 3rdSD = m-3d - 2%

Statement I

68% of the values lies within m+d and m-d

This mean 34% of values lies within the 1st SD above the mean and 34% lies within 1st SD below the mean.

We have to find the percentage greater then 1st SD above the mean

50%-34% = 16%

Therefore sufficient.

Statement II

16% of the values are less than m-d

Therefore 16% of the values would be more than m+d.

Therefore sufficient.

Hence D is the answer.

Let me know if you have any doubts.

wow that's great to know. Thanks