(a) in the case of 1[ trade apprentices] who, having undergone institutional training in a school or other institution recognised by the National Council, have passed the trade tests 2[ or examinations] conducted by 3[ that Council or by an institution recognised by that Council], the period of apprenticeship training shall be such as may be determined by that Council;

(aa) 4[ in the case of trade apprentices who, having undergone institutional training in a school or other institution affiliated to or recognised by a Board or State Council of Technical Education or any other authority which the Central Government may, by notification in the Official Gazette specify in this behalf, have passed the trade tests, 2[ or examinations] conducted by that Board or State Council or authority, the period of apprenticeship training shall be such as may be prescribed;]

(b) in the case of other 1[ trade apprentices], the period of apprenticeship training shall be such as may be prescribed;

(c) 4[ in the case of graduate or technician apprentices, 5[ technician (vocational) apprentices] the period of apprenticeship training shall be such as may be prescribed].