Environmental cracks are often branched and can propagate along the grain boundaries or across the grains. Which terms fill the blanks?

• A. Intergranular, Transgranular
• B. Transgranular, Intergranular
• C. Along grain boundaries, Across grains
• D. Diffuse, Concentrated

Answer: (A)

Crack propagation paths in metals are described by two standard terms: intergranular for cracking along grain boundaries, and transgranular for cracking through the grains themselves. The statement mentions environmental cracks that can branch and propagate along grain boundaries or across grains, which aligns with using intergranular for the along-boundaries part and transgranular for the across-grains part. The other options use nonstandard phrasing or refer to concepts like diffusion instead of the actual path of crack growth, so they don’t fit as well.