How does Block 4 improve the radar cross-section of the fighter?

The radar cross-section (RCS) of a fighter aircraft refers to how detectable it is by radar. Block 4 improvements significantly enhance the RCS through design modifications and the use of advanced materials that minimize radar reflections. These upgrades often involve changes to the aircraft's shape and surface coatings, which are specifically engineered to absorb or deflect radar waves, thereby decreasing the likelihood of detection by enemy radar systems.

In contrast, enhancements such as increased engine power or weight reduction may contribute to performance or efficiency but do not directly affect radar visibility. Similarly, while visual camouflage patterns might help in evading visual detection, they do not have an impact on radar signatures. Therefore, the correct answer focuses on the technological advancements in design and materials that directly address the challenge of radar detection.