Since 1991 the infant mortality rate and that of children under five years of age have declined at an annual rate of 4.6 percent and 4.9 percent.是什么意思_Since 1991 the infant mortality rate and that of children under five years of age have declined at an annual rate of 4.6 percent and 4.9 percent.在线翻译_英语_读音_用法_例句