Rewrite the sentence in indirect speech.
Prabha said to Prabhu, "Prem was playing cards."

Correct option is A

Explanation: The past continuous tense "was playing" in direct speech becomes "had been playing" in indirect speech to indicate the ongoing action in the past at the time of the original statement.
Grammatical rule used: Past continuous changes to past perfect continuous in indirect speech to indicate an action ongoing in the past prior to another past action or time.
Example: "He was working on the project," she said to him. -> She told him that he had been working on the project.