This question attracted nearly all the candidates. Part (a)(i) was the sketch of a simple carburettor. Some of the candidates mixed up the naming of the parts. The correct naming is given below.
(a)
(i) p is choke or strangler
q is float chamber
r is needle valve
5 is float
t is jet
u is throttle valve or butterfly valve

(ii) The functions of the named parts are
- Choke or strangle valve is used to provide rich mixture for cold starting Float chamber accommodates fuel from the pump, float and needle valve.
- Needle valve controls the amount of fuel entering the float chamber.
- Float regulates the level of fuel inside the float chamber.
- Jet meters the correct amount of fuel from the float chamber and discharges it into the mixing chamber.
Throttle valve regulates the amount of air-fuel mixture that goes into the engine.
(b)   The gases are
(i)   Carbon-dioxide (C02)
(ii) Nitrogen (N2)
(iii)   Water vapour (H20)