Why did the peace talks break down in 1972?

The refusal to continue came during the 138th session of the peace talks. U.S. delegate William Porter angered the communist negotiators by asking for a postponement of the next scheduled session of the conference until December 30, to give Hanoi and the Viet Cong an opportunity to develop a “more constructive approach” at the talks.

The U.S. side was displeased with the North Vietnamese, who repeatedly demanded that South Vietnamese President Nguyen Van Thieu resign as a prerequisite for any meaningful discussions. Although both sides returned to the official talks in January 1972, the real negotiations were being conducted between Henry Kissinger and Le Duc Tho, the lead North Vietnamese negotiator, in a private villa outside Paris. These secret talks did not result in a peace agreement until January 1973, after the massive 1972 North Vietnamese Easter Offensive had been blunted and Nixon had ordered the “Christmas bombing” of Hanoi and Haiphong to convince North Vietnam to rejoin the peace negotiations.

The answer b is correct this all occurred during the red scare