A sizeable number of Candidates who attempted this question could not identify the component and name the labelled parts.
The solution to the poorly answered part of the question is given below.

(a)        (i)         Bellow thermostat, Thermostat          
(ii)        Naming parts labelled

U:        Valve seat
V:        Jiggle valve, Jiggle pin
W:       Bellow

(iii)       Working principle of bellows type thermostat

Cold Engine:   Under cold conditions, the valve is held close down to its seat by the contraction of the bellows and no water can pass from the cylinder head to the radiator.
Hot Engine:     As the water in the jacket is heated, the volatile liquid in the bellows is converted into vapour. This causes each bellow to expand and the total expansion lifts the valve from its seat. The water can now flow from the cylinder head to be cooled in the radiator, that is, circulation is started. When the engine is switched off, the valve is pulled down to its seat, by the contraction of the bellows as the vapourised alcohol is converted to liquid by the lower temperature until it is fully closed down when the temperature has fallen below 77 degrees centigrade.