Transition metals have high melting point due to their high enthalpy of atomisation. They form strong metallic bonds with unpaired electrons.
Melting point of Ag=961.8∘C
Melting point of Cs=28.5∘C
Melting point of Ga=30∘C
Melting point of Hg=−38.83∘C
Cs,Ga and Hg are liquid at or near room temperature.
Among the given options Ag has the maximum Melting point, as it belongs to transition metal series.