A submersible temperature sensor takes temperature readings at three different depths in a lake.

Which data set is the most precise ?
A 15 m depth: 18, 16, 20.0
B 25 m depth: 15.6C, 15.6C, 15.9C
C 5 m depth: 24.5C, 20.C,21.C
D 35 m depth: 12.0C, 18.1C, 14.2C