[Grammar] I met a girl, whom John had talked about.

[wotcha]

1. I met a girl whom John had talked about.

2. I met a girl, whom John had talked about.

3. I have a dog whose tail is red.

4. I have a dog, whose tail is red.


I wonder if it is possible to put period before 'whom' and 'whose' as you can see in 3 and 4.

 

[SlickVic9000]

(Not a Teacher)

I don't see any need to put an apostrophe in these sentences.

 

[Raymott]

(Not a Teacher)

I don't see any need to put an apostrophe in these sentences.

I agree. Neither do they need the comma that the OP has put there, nor the period they've asked about.

For 1. I'd write:
"I met the girl [who/whom] John talked about." (If John talked about only one girl.)
"I met one of the girls [who/whom] John talked about." (If John talked about more than one girl.)

I wouldn't really use either who or whom.