Concept:Birth rate increases when measures encourage more childbirths or protect pregnancies.Explanation:Encouraging early marriages increases the number of childbearing years, so it raises birth rate.Encouraging polygamy increases the number of married women of childbearing age, so it raises birth rate.Legislation against abortion reduces pregnancy termination, so it raises birth rate.Encouragement of less work hours does not directly increase childbirth or birth rate; it is not a recognised pronatalist policy.Answer:B. Encouragement of less work hours