Answer:
The correct answer is that the manufacturers of the national brands could not sell all the output under their own brands.
Step-by-step explanation:
Private label is defined as those products which are produced or manufactured through one company for the purpose of sale under another brand of the company.
So, the manufacturers of the national brands find difficult in selling the products manufactured by them under their own labels until they establish their place in the market. Therefore, in order to establish themselves first, they need to produce the products under the private labels, and sell them.