VI. Fill the blanks with the correct forms of the verbs:
1. Teenagers now (prefer)______________ chatting on the computers with their friends to meeting face to face.
2. I (not have)_________________________ enough sleep last night, so I'm very tired now.
3. Since we first met at the conference, Jessica (encourage)___________________ me a lot in my career choice.
4. I (be)____________________ to Spain twice, but I haven't visited Barcelona yet.
5. For centuries, nature (inspire)__________________ many scientists and inventors in their great inventions.