21. When carbon is added to iron in proper ________ the result is steel.

A) rates B) thicknesses C) proportions D) densities

22. You should try to ________ your ambition and be more realistic.

A) reserve B) restrain C) retain D) replace

23. Nancy is only a sort of ________ of her husband‘s opinion and has no ideas of her own. A) sample B) reproduction C) shadow D) echo

24. Now that spring is here， you can _____ these fur coats till you need them again next winter.

A) put over B) put away C) put off D) put down

25. There is a ________ of impatience in the tone of his voice.

A) hint B) notion C) dot D) phrase

21-25 CBDBA