Put the verbs in the correct form in the affirmative sentences. They (to have) dinner in Washington, DC, the USA.

The correct answer is 'had'. Explanation: The sentence describes a past action. The simple past tense of 'have' is 'had'. The sentence becomes: They had dinner in Washington, DC, the USA. Other options are incorrect: * 'have had' is present perfect tense. * 'has had' is present perfect tense, used with singular subjects (he/she/it). * 'were had' is grammatically incorrect. Therefore, the answer is 'had'.