21．The TV sets made by our factory sell best，but 10 years ago no one could have guessed the place in the markets that they________.
A．were having B．had had
C．were to have D．had
22．Online paperchecking requires that more attention________.
A．be paid to spelling
B．to be paid to spelling
C．should pay to spelling
D．and spelling be paid to
23．He waited for about two hours，only________to come the next day to meet the manager.
A．to tell B．to be told
C．telling D．having been told
24．They kept trying，and their efforts finally________.
A．make it B．paid off
C．are made it D．are paid off
25．________at the airport，he telephoned his wife and told her what he would do when he got home.
A．Once arrived
B．As soon as he reached
C．When he got
D．Upon arriving
