Most of the candidates had difficulty answering the part  (a).  Other parts of the question posed no difficulty.  The required response to part (a)  is given below:

-           fittings for acetylene gas cylinders are painted red, while those for oxygen cylinders are painted black;

-           fittings for acetylene fuel gas cylinders have left-hand thread while those of oxygen cylinders have right-hand threads;
            -           acetylene gas cylinders are shorter than oxygen gas cylinders.