Two plates identical in size, one of black and rough surface (\[{{B}_{1}}\]) and the other smooth and polished (\[{{A}_{2}}\]) are interconnected by a thin horizontal pipe with a mercury pellet at the centre. Two more plates \[{{A}_{1}}\] (identical to\[{{A}_{2}}\]) and\[{{B}_{2}}\] (identical to\[{{B}_{1}}\]) are heated to the same temperature and placed closed to the plates \[{{B}_{1}}\] and \[{{A}_{2}}\] as shown in figure. The mercury pellet

• A. moves to the right
• B.  moves to the left
• C.  remains stationary
• D.  starts oscillating left and right