Choose the correct variant. Bob said, "I didn't watch this film yesterday." Bob said that he ... that film the day before.

The original sentence is in the past simple tense. When reporting speech, if the reporting verb is in the past tense (e.g., 'said'), the tense in the reported clause usually shifts back. 'I didn't watch' (past simple) becomes 'hadn't watched' (past perfect) in reported speech. Therefore, the correct option is 'hadn't watched'.

Answer: hadn't watched