meta-center

center of pressure

center of buoyancy

center of gravity

the metal piece will simply float over the mercury

the metal piece will be immersed in mercury by half

whole of the metal piece will be immersed with its top surface just at mercury level

metal piece will sink to the bottom

the nature of the liquid and the solid

the material which exists above the free surface of the liquid

both of die above

any one of the above

force of adhesion

force of cohesion

force of friction

force of diffusion

viscosity

air resistance

surface tension forces

atmospheric pressure