Complete the sentence with the correct form of the verb in brackets: "He has ____ (spell) my surname wrongly on every letter."

Explication

The perfect has needs a participle, and this verb keeps two of them. Spelt is the familiar British -t form; spelled is the standard one in American English and is widespread in Britain, so both finish the sentence. The -ed form here is a codified past form of an irregular verb, not a learner's regularisation, which is why it counts as fully correct.