The scale 1:20000 means that 20000cm of the actual ground is represented by 1cm on the map.
In other words 1cm distance in the map is equal to 20000cm of distance in the actual ground.
Therefore we can say;
3.8cm on map = `3.8xx20000` cm on actual ground
3.8cm on map = 76000cm on actual ground
`1km = 1000m = 1000x100cm = 100000cm`
`76000cm = 76000/100000km = 0.76km`
So the answer is 0.76km. It is in answer option B.
The answer is option B, 0.76km.