若2abn+1与-am-1b2是同类项,则m+n=______,nm=______.
由同类项的定义可知n+1=2且m-1=1,
解得n=1,m=2,
所以m+n=3,nm=1.
With the death of Libyan leader Muammar Gadhafi on Thursday, the country's new leaders ______ the challenge of rebuilding a war-torn nation. [ ]
A. faced
B. are facing
C. had faced
D. is faced
简述布鲁姆关于教学目标的认知目标层次。