Answer: Wednesday
Step-by-step explanation: Think of it like this; all temperatures are cold for us human beings. The question is being asked which days did Elizabeth record the lowest (coldest) temperature.
You can put this figures into a number line. Any number going to the right of a number line is an increase. So Monday and Tuesday can be eliminated. Any number going the left of a number line is decreasing. - 5 is very cold but -20 is colder than -5. Therefore, the lowest (coldest) temperature is -20 which was Wednesday,
Hope this explanation helps.