Fill in the blank with appropriate preposition:

He gets___ well with his colleagues.

The most appropriate preposition to fill the blank is along. Here's why: Along indicates a harmonious relationship or ability to work and interact well with others. It's a common preposition used in this context. Other prepositions like "at," "by," or "with" could be grammatically correct but don't convey the same meaning as effectively. Therefore, "He gets along well with his colleagues" is the most natural and grammatically correct sentence.