Concept:Birth rate is the number of live births per 1,000 people in a year. It is high when many pregnancies are not planned or prevented.Solution:When birth control (family planning) measures are ineffective, many unplanned pregnancies occur, so more babies are born and the birth rate rises.Effective use of contraceptives (A) lowers the birth rate. Drift of the youth to towns (B) and failure to acquire skills (D) cause other problems (urban congestion, unemployment), not high birth rate directly.Answer:Option C (ineffective birth control measures)