Step 1: The Factories Act regulates employment age and working hours in factories. Test each statement against these provisions.
Step 2: The Act prohibits employment of children below 14 years of age, and classifies persons aged 15 to 18 years as adolescents who need a fitness certificate before they can be employed. This makes option (b) correct.
Step 3: Working hours are capped, not extended - the Act prescribes a maximum of 48 hours per week, not exceeding 9 hours per day, with at least half an hour of rest after 5 hours of continuous work. So 72 hours and 82 hours per week (options c and d) are both wrong.
Step 4: Option (a) is invalid because child labour under 14 is banned, so the premise of earning more from serious work does not apply. Hence the correct statement is (b).