Bargaining impasse occurs when:

A) either party to negotiations violates the NLRA.
B) bargaining partners fail to agree on mutually acceptable terms of employment.
C) bargaining partners engage in concession bargaining.
D) a new contract is not agreed upon before the old contract expires.

Bargaining impasse occurs when bargaining partners fail to agree on mutually acceptable terms of employment. This means that they have reached a stalemate in negotiations and are unable to move forward towards a mutually acceptable agreement. It is important to note that while bargaining impasse is a common occurrence in labor negotiations, it can have negative consequences for both employers and employees if not resolved.