Answer:
At -20°C the mercury state will be liquid
Step-by-step explanation:
The melting point of a substance is the temperature at which it changes from solid state to a liquid state, and the boiling point is the temperature at which it changes from liquid state to a gaseous state.
If mercury melts at -39°C and boils at 356.9°C, it means that if the temperature is lower than -39°C, mercury will remain al solid state. Between -39°C and 356.9°C, the state of mercury will be liquid and, above 356.9°C mercury will remain at gaseous state.
So, at -20°C the mercury state will be liquid, because that temperature it is between -39°C and 356.9°C.