Horizontal collaboration refers to a relationship that is and/or
a. 3pls to 3pls and/or service provider to service provider.
b. buyer to buyer and/or seller to seller.
c. flat across the chain and/or involving partners equal in size.
d. collaboration with horizontal and/or vertical competitors.

B. Buyer to buyer and/or seller to seller.

Explanation:

Horizontal collaboration is when manufacturers share supply chain assets for mutual reasons.

It is collaboration across the supply chain. Furthermore, horizontal collaboration is between companies  market and sell to similar customers and consumers if they dont compete directly. A good example of horizontal collaboration involves the Hershey Co. and the Ferrero Group in North America. The two companies have collaboration in terms of warehousing, transportation etc.

Its a business strategy by manufacturers to further strengthen partnership and market penetration to customers and consumers

A, C, D is not the answer, But b perfectly depicts th explanations i have given above.

answer; sensory adaptation;