I wish I . . . . . . . a millionaire. A. am B. are C. was D. were

The correct answer is C. was.

The sentence “I wish I was a millionaire” is in the past tense because it is expressing a wish that is not currently true. The speaker is wishing that they were a millionaire, but they are not currently a millionaire.

The other options are incorrect because they are not in the past tense. Option A, am, is in the present tense. Option B, are, is also in the present tense. Option D, were, is in the past participle form, which is used to form the perfect tenses.

In conclusion, the correct answer to the question “I wish I . . . . . . . a millionaire” is C. was.