Although the growth in Canada's population had slowed down by 1966 (the increase the first half of the 1960's was only nine percent) , another large population wave was coming over the horizon. It would be composed of the children who were born during the period of the high birth rate prior to 1957. The phrase "prior to" is closest in meaning to which of following? (A) behind (B) since (C) during (D) preceding