The correct answer is: B. arrived/was waiting
Shannon was waiting for Sakura at the theatre for more than an hour. When Sakura finally arrived, Shannon was angry because he had been waiting for her for so long. The use of the past continuous tense (was waiting) indicates that Shannon was in the act of waiting when Sakura arrived. The use of the simple past tense (arrived) indicates that Sakura’s arrival was a completed event.
A. had arrived/was waiting is incorrect because it implies that Shannon was waiting for Sakura before she arrived. This is not supported by the information in the question.
C. had been arriving/was waiting is incorrect because it implies that Shannon was in the act of arriving when Sakura arrived. This is not supported by the information in the question.
D. was arriving/waited is incorrect because it implies that Shannon was waiting for Sakura while she was arriving. This is not supported by the information in the question.
E. arrived/had been waiting is incorrect because it implies that Shannon was waiting for Sakura for more than an hour before she arrived. This is not supported by the information in the question.