Well, I've had a doubt for use which and that. Tell me if these examples are correct:
This is the hot dog which I made.
This is the hot dog that I made.
I'm finding the DVD which I lost.
I'm finding ...
A1. The dogs, which barked in the night-time, did not recognize the thief.
A2. The dogs which barked in the night-time did not recognize the thief.
B1. The dogs, that barked in the night-time, did not ...
The department shredded all the files from the inquiry which contained embarrassing material.
After having read the sentence above, I was wondering if the department destroy every file, or only those ...