These hard questions ask you to explain choices you would make while preparing a real report. Read the stated requirement before selecting an answer. The business key, output grain and missing-value policy usually matter more than the name of a ribbon command.
Each question includes a specific misconception, such as treating identifiers as quantities or assuming a lookup key is unique. Use the hint only after you have traced a small example yourself. After checking, read the explanation and try the matching practical lessons in the course. The questions use original fictional situations. They are practice for an interview discussion, with checked decisions rather than a claim about what every employer will ask.