Use the present perfect to make true sentences for you.
1. write a letter in English
2. phone the emergency services
3. lose your mobile
4. forget to post an important letter
5. buy a book online
6. have a virus on your computer

1. I haven't written a letter in English. 2. I haven't phoned the emergency services. 3. I haven't lost my mobile. 4. I haven't forgotten to post an important letter. 5. I haven't bought a book online. 6. I haven't had a virus on my computer.