Electrical conductivity tester.
If the bulb begins to glow brightly when the plug is submerged in the unknown solution then the solution has high conductivity.
The bright glow of the bulb resulting from the experiment indicates that the current flows easily through the unknown liquid.
Mammals are adapted to live in D - all of the above. Mammals are, infact, very versatile groups of species which have evolved in a way that also itself enables their versatility. For this reason, mammals have been able to roam the different parts of Earth and thrive in that environment.
