Complete the following dialogues with an appropriate preposition.

1. A: I'm so sorry you're leaving.
B: Me too - but we'll keep ...... touch.

2. A: I'm calling to check on my pizza order - it hasn't been delivered yet.
B: I'm sorry - did you order ..... phone or ....... person?

3. A: Can I contact you ..... email?
B: Yes, of course - I'll give you my email address.

4. A: Steven's missed a lot of classes lately.
B: Has he? Maybe we should have a word ....... him.

5. A: How did you two get to know one another?
B: Actually, we met ...... a friend.

6. A: Have you known each other long?
B: Yes, we've been going out ...... one another for a year. ​