Complete the sentences with the Present Perfect form of the verbs in brackets.
1. He _____________________________ (not call) his friend. 2. John _____________(write) a letter to his sister. 3. The children __________________ (clean) the forest. 4. She _____________________________ (not walk) the dog. 5. They _________________________ (buy) a new computer. 6. I ____________ (leave) the book at home.