If Helen             her credit card, she could have bought the dress.

Xiao Ming speaks English very well as if he ____ an Englishman.

Tom’s mother often requires that he       more time in studying English every day．

— What has happened to Tom ? — I don''t know . He ____ lost . 

“I know she was in because I heard her radio, but she didn’t open the door.” “She___the bell.”