Piyush behaves strangely at times and, therefore, nobody gets ...... with him.

Answer: Option C

Piyush behaves strangely at times and, therefore, nobody gets along with him.
In this context, "gets along with" means to have a harmonious or friendly relationship with someone. The phrase indicates that because of Piyush's strange behavior, others find it difficult to establish a rapport or bond with him. Therefore, "along" is the most appropriate choice to complete the sentence, conveying the idea that nobody can develop a smooth relationship with Piyush due to his peculiar actions.