题干
As China grows stronger and stronger, Chinese _____ in more and more schools out of our country.
A：teaches
B：is taught
C：has taught
D：was taught
答案(点此获取答案解析）
B
=(cos
π, sin
, 
，若△OAB是以O为直角顶点的等腰直角三角形，则△OAB的面积等于（ ）