A:30 N/m
B:50 N/m
C:300 N/m
D:500 N/m
— Jack, will your family move to Shanghai?
— Yes. That's a very big ________ my parents made.
经过30多年的不懈努力,深圳迅速从一个边陲小镇发展成为一个现代化大城市,综合经济实力跃居全国大中城市前列。这充分证明了( )