What is needed in order to reject a weld for accumulation of discontinuities (AI)?

The correct answer revolves around the specific criteria outlined in the context of weld acceptance and rejection based on the accumulation of discontinuities. When evaluating a weld for potential rejection due to discontinuities, the aggregate length of those discontinuities plays a crucial role.

The requirement that the aggregate length must exceed a certain measurement, specifically 2", signifies that a significant amount of discontinuity is present within a given weld area, which can compromise the integrity and performance of the weld. The presence of any discontinuity, regardless of its type, contributes to the potential rejection of the weld if it accumulates to this extent.

While the other choices mention factors such as multiple different types of discontinuities or specific indications like incomplete penetration, these alone do not provide a basis for rejection without the context of their length or total impact on the weld. The focus on aggregate length gives a quantifiable measure that is critical in determining the quality of the weld, hence solidifying why option B is seen as the correct criterion for rejection in this situation.