21. Because of her illness, Helen has been absent from school for three days     .

A. in a row               B. in the row             C. for a row              D. over a row

22. In the early twentieth century, Australia    the USA of the eighteenth century.

A. is resembled          B. in resembling        C. resembled             D. resemblance

23. The twins are so alike that no one can     one       the other.

A. distinguish; from                                  B. distinguish; between

C. distinguishes; from                                D. distinguishes; between