Li
Ga
Cs
Br
The given question asks which element among the options will remain as a liquid inside pure boiling water. To solve this, we need to know the boiling point of each element and compare them to the boiling point of water, which is 100°C at standard atmospheric pressure.
From this analysis, we can conclude that Gallium (Ga) is the element that remains as a liquid inside pure boiling water. Hence, the correct answer is Ga.