Near the very end of freezing, the last bit of liquid left between grains is enriched with the impurities and alloying elements that got pushed out ahead of the growing solid, so it stays molten at a lower temperature than the surrounding metal. This thin liquid film has essentially no strength. If the casting or weld is shrinking and cooling at that moment while being restrained, it pulls the grains apart across that weak film because there is nothing to resist the tension there. So it takes both the segregated low melting film and a pulling stress at the same time to tear the metal, which points to option (D), segregation together with tensile stress.