题干
—Do you want to read this book?
—Well, I it already．
—Well, I it already．
A：read
B：have read
C：am reading
D：will read
答案(点此获取答案解析）
B
)通过时的轨迹如右图实线所示，a、b为两个等势面，则下列判断中正确的是( ).