The correct answer is C. Last week a new shirt was bought by me.
A. Last week a new shirt was bought by I. is incorrect because the subject and verb do not agree in number. The subject is “I,” which is singular, but the verb is “was bought,” which is plural.
B. Last week a new shirt is bought by I. is incorrect because the verb tense does not agree with the time reference. The sentence states that the shirt was bought last week, but the verb “is bought” is in the present tense.
D. Last week a new shirt had been bought by me. is incorrect because the verb tense is too complex. The sentence states that the shirt was bought last week, so the verb tense should be simple past tense.
The sentence “I bought a new shirt last week” is in the simple past tense. The simple past tense is used to talk about events that happened in the past and are not happening now. In this case, the event is the purchase of the new shirt. The sentence states that the shirt was bought last week, so the verb tense should be simple past tense.