we can approach the question in this way:
say there are 100 inhabitants
1.) 20 inhabitants have height atleast 2 m.
2.) 20 inhabitants have height atmost 1.5m
3.) 60 people have height between 1.5m and 2m
Consider the lower limit of height in case 1. It is 2m.(upper limit is infinity)
In case 2 the lower limit can be 0.(upper limit is 1.5m)
In case 3 the lower limit is 1.5m(upper limit 2m)
On taking the average of minimum values:(as the options are comparing values of heights <= or >=)
2 x 20+0 x 20+1.5 x 60 = 130
So lower limit of height is : h>=1.3
So answer is option A