若1是方程x2-2x-m=0的根，则m = ．
-1
把x=1代入方程解得m =-1
劳动保护、安全生产是社会稳定、家庭幸福的重因素。
The scientist told the reporter that only after he went abroad ______ what his motherland meant to him. [ ]
A. he realized
B. did he realize
C. had he realized
D. he had realized
