如图体现的我国地形特征是( )
A:地形复杂多样
B:地形平坦
C:地势西高东低
D:地势呈阶梯状分布
直线y=12x+k与x轴、y轴的交点分别是A,B,且S△AOB≤1,则k的取值范围是( )
After the education reform(改革) in Jiangsu Province, the pupils have_______ time to relax and _______ homework to do.
如图,在等边三角形ABC中,点E、F分别是AB、AC的中点,EF=4,△ABC的周长为____