The words, 'yesterday morning' indicates that the verb in the sentence is in past tense.
Option A is incorrect as 'am being' is a verb in present continuous tense.
Option B is incorrect as 'am' is a verb in simple present tense.
Options C: The verb 'was being' is in past continuous time. Past continuous tense is used to denote an action, which was going on at some time in the past. It cannot indicate an action which happened at a particular time of 7.00 a.m. in the past. Hence, this option is incorrect.
Option D: The verb 'was' is in simple past tense. The simple past tense is used to indicate an action completed in the past. The particular time, 7.00 a.m., indicates the time when the action happened in the past. Hence, this option is correct.