Choose the correct form of adjective for the given sentence:
These books are a _____ improvement on what has gone before.

- Adjective serves as a modifier of a noun to denote a quality of the thing named, to indicate its quantity or extent, or to specify a thing as distinct from something else.
- Great: of an extent, amount, or intensity considerably above the normal or average.
- Example: The article was of great interest.
- Therefore, it is clear that great is the most appropriate answer.
- Hence, option 4 is the correct answer.
- The correct sentence is: These books are a great improvement on what has gone before.