The best thermometer to use where temperatures drop below -39°C (-38.2°F) is:.

The best thermometer to use for this temperature is the alcohol-in-a -glass thermometer.

Explanation:

The alcohol thermometer is a type of thermometer which uses ethanol as its thermometric liquid. This has some advantages at low temperatures because ethanol freezes at about −114.9 °C  that is (−174.82 °F).

Due to its low freezing point, it can still function effectively as a thermometric liquid, expanding and contracting properly based on the applied heat,  when dealing with temperature measurements that are at about -38.2°F.

indicate valleys, hills, steepness and gentleness of slopes.

explanation:

contour lines on a map indicate elevation, or depth. numeric notations on contour lines refer to the level of elevation, or height about sea level.