From the words lettered A to D, choose the word or group of words that best completes each of the following sentences. He sent a card to his parents to cong...

From the words lettered A to D, choose the word or group of words that best completes each of the following sentences.
He sent a card to his parents to congratulate them......their diamond wedding anniversary

Answer Details

The correct option is "on". "On" is the most appropriate preposition to use when congratulating someone for an achievement or milestone, such as a wedding anniversary. Therefore, the sentence should read: "He sent a card to his parents to congratulate them on their diamond wedding anniversary."