21. back up

　　1) 累積

　　The subway is running behind schedule. and traffic is backed up for blocks. I dont know if well make the 6:30 show.

　　2) 支持

　　Ill back it up.

　　22. be bound for 到地方

　　The bus is bound for New England.

　　23. be (feel) myself 找到自我

　　Im feeling myself again.

　　24. be burned up 生氣

　　She was really burned up at the news.

　　25. be hard up for

　　Im hard up for clothes, but I have a lot of books.

　　26. be head and shoulders above 好許多

　　In calculus. Joe is head and shoulders above his classmates.

　　27. be in the dark 蒙在鼓里

　　A: Do you have any idea what his notice is about?

　　B: Im as in the dark as you are.

　　28.be stuck 卡住了

　　I cant get this window open. Its stuck.

　　29. bite off more than one can chew. 貪多嚼不爛

　　A: I hear youre taking an advanced physics course this semester.

　　B: I think Ive bitten off more than I can chew.

　　30. break new ground 有了新的突破

　　His architectural design broke new ground in the field.