As the students gain (confident) ______ in themselves, they are less likely to cheat.

As the students gain (confident) ______ in themselves, they are less likely to cheat.

The correct word to complete the sentence is confidence.

So the sentence would read:

"As the students gain confidence in themselves, they are less likely to cheat."

"Confidence" fits here because it refers to a belief in one's own abilities, which aligns with the idea of students being less likely to cheat if they trust themselves more.