What is the main argument of critics of the win–win negotiation tactic?

a. Parties show the same level of concern for the relationship.
b. Party with the least interest in the relationship has less power to negotiate.
c. Parties show concern for other but not for selves.
d. It is doubtful both parties have the same level of concern for relationship.

d. It is doubtful both parties have the same level of concern for relationship.