Why Would Firms Use the Practice of Tying

Why would firms use the practice of tying?

A) It allows firms to tie goods that are highly valued together with goods that are not highly valued, hence increasing profits
For firms.
B) It is a way to force consumers to buy more than what they would without tying.
C) It is a subtle way to raise prices for those consumers who have a low willingness to pay.
D) It is a subtle way to charge higher prices to those consumers with a high willingness to pay, and a lower price to consumers
With a low willingness to pay.