16. If he doesn't talk much in class, he can't understand the lesson
17. It is such heavy chair that he can't move it 

S + V + such + Adjective + Noun + that + S + V

18. After he has a light breakfast, he went to work
19. If I don't arrive, I can't go to her wedding
20. If the text is difficult, I can't finish it on time
     The text is too dificult to finish it on time
     I can't finish the text because it is very difficult
    The text is very dificult, so I can't finish it on time
21. He isn't tall enough to play basketball
      He is so short that he can't play basketball.
      If he is short, he can't play basketball
22. Though Tom was very lazy, he passed the final exam as well