A:snake
B:lion
C:zebra
如图是光源S经平面镜反射的两条光线,请画图确定光源位置,并完成光路图.
读句子,选择适当的词组完成句子。
more than having a barbecue in danger on foot keep quiet
Who does this pencil-box belong __________?
设集合M={-1,0,1},N=x|x2=x,则M∩N=( )