Which configuration allows a backhoe loader to dig a depth of 6.8 inches below grade?

The loader configuration is specifically designed for lifting and loading operations, which includes the capability to adjust the position of the loader arms to achieve varying depths. In this configuration, the backhoe's bucket can be angled and positioned to dig effectively, allowing it to reach depths such as 6.8 inches below grade. This capability is essential for tasks like excavation and loading materials.

The other configurations—clamshell, scraper, and dozer—are tailored for different functions. The clamshell configuration is more suited for digging and scooping with a gripping action, while the scraper configuration is designed for moving earth across a site efficiently. The dozer configuration focuses on pushing material rather than digging with precision at specified depths. Thus, while all these configurations have their unique advantages, the loader configuration is the most appropriate choice for achieving the specific digging depth stated in the question.