A:
B:
C:
D:
—Why are you standing(站立), Alice?
—I can't see the blackboard(黑板 ) clearly(清楚地) . Two tall boys are sitting _____________ me.
①f(x)=x2(x≥0);
②f(x)=ex(x∈R);
③f(x)= 4xx2+1 (x≥0);
④f(x)= loga(ax−18)(a>0,a≠1) .
关于物理概念的建立和物理规律的形成,下列说法不正确的是
以下对动物特征的描述不正确的是( )