Which engines are equipped with E tools?

The option indicating that engines 4, 5, and 6 are equipped with E tools is correct because these specific engines have been designed or modified to utilize E tools effectively. E tools enhance performance and functionality, and in this case, engines 4, 5, and 6 may have advanced systems or configurations that allow for optimal integration with these tools.

In the context of truck skills or maintenance, knowing which engines are equipped with E tools is crucial for understanding which vehicles can utilize these enhancements for improved efficiency or capabilities. The other engines listed, while they may perform well, do not feature the necessary adaptations to support E tools fully, which can limit their operational flexibility compared to those in the correct choice.