I/ Choose the correct answer (A, B, C or D) to complete the sentences: 21. ______ is the longest river in Viet Nam, Mekong River or Dong Nai River? A. Where B. Which C. How D. Who 22. If we cut down more forests. there ______ more floods. A. are B. were C. have been D. will be 23. Here is their son's telephone number; I don't have _______ A. their B. theirs C. they D. them 24. A robot can do _______ different things from looking after a baby to building a house. A. much B. many C. few D. little 25. Lake Baikal is the _______ freshwater lake in the world. A. large B. larger C. largest D. more large