Explanation: The verb 'to be' (was/were) must agree in number with the subject. 'Was' is used for singular subjects (I, he, she, it), and 'were' is used for plural subjects (we, you, they). In sentences 1, 5, and 8, the subjects are singular, so 'was' should be used. In sentences 2, 4, 6, and 7, the subjects are plural, so 'were' should be used. In sentence 3, 'I' is a singular subject, so 'was' should be used.