Which of the following is a common type of weld defect?

Cracking is indeed a common type of weld defect that occurs when the welded material fails due to a variety of factors such as thermal stresses, improper filler material, or issues related to the base metal. It can manifest in different forms, including hot cracks, cold cracks, and reheat cracks, depending on the conditions under which welding is performed and the materials being used. Understanding cracking is crucial for welders because it can significantly weaken the integrity of the welded joint and compromise the overall quality of the weld.

The other listed defects, although not chosen as the answer, are also recognized issues in welding processes. Burn-through occurs when excessive heat causes a hole to form in the base material, and excessive spatter involves the uncontrolled scattering of molten metal during the welding process. Each of these defects can affect the quality of the weld and would warrant a welder's attention to ensure strong and reliable joints. Thus, while cracking is a significant concern, the presence of burn-through and spatter also highlights the need for careful technique and monitoring during the welding process.