A:carefully; carefully
B:carefully; careful
C:careful; carefully
矩形ABCD中AB=6cm,BC=8cm,AE平分∠BAC交BC于E,CF平分∠ACD交AD于F.
①说明四边形AECF为平行四边形;
②求四边形AECF的面积.
下列图象中有关量的变化趋势与对应叙述关系正确的是( )
选择相应的应答语( )
下列说法正确的是( )