"true or false: muzzle grabbing between parent and offspring is followed by a pup moving closer to and engaging in affiliative behaviors with the parent."

I believe the answer is: True

For mature dogs, muzzle grabbing is a method to convey their love.
For a pup, muzzle grabbing serve as two functions, to reciprocate with their parents love and to strengthen their teeth structure.
 Dogs also do this for humans that they cherish. If you're a dog owner, you'll notice that once in a while, they would try to put your arms into their mouth, this is another form of the muzzle grabbing.