①公平是社会稳定的"天平”
②公平是维系良好合作的前提
③公平一直是人类孜孜以求的目标
④公平的社会为人的发展提供同样的权利和机会
A:①②
B:①④
C:②③
D:③④
At the beginning of the 20th century, many people thought that the family was falling apart—__________, they thought it was dying. ( )
若x,y为实数,且,则=____ 。