Answer:Creation of two-way forest trust
Explanation: In active directory, Two way forest trusty is the two way trusting condition where one forest trust the other forest and it works same for both forest.The forest domain of one forest is reliable and have trusty relationship with the other forest and vice-versa.
This function of the forest helps all the users to reliably access all the components of both the domains.Thus two-way forest trust should be created between the two organization mentioned in the question.