Ответ:

1. Have you met my cousin greg?

but i have heard he's very friendly...

2. Samantha has traveled... but she has never visited venice

3. Has Charlie ever had a pet? ... but he has always wanted a dog

4. ...the only thing hasn't done is check...

1. A. Have you met.......

B. have heard

2.has travelled,has never visited

3. A. Has Charlie ever had a pet?

B. No, he has always wanted a dog.

4. haven't done