**Core Concept:** Past perfect tense (had + past participle) is used to indicate an action completed before another past action. **Analysis:** - **Correct Answer (B):** 'By the time... was published' establishes a past reference point. The company's action (implementing policies) occurred before this point, requiring the past perfect tense. - **Error Options:** - A (has implemented): Present perfect tense refers to actions continuing into the present, incompatible with a past event. - C (implements): Simple present tense mismatches the past context. - D (implemented): Simple past tense does not show the action occurred before another past event. **Common Mistake:** Confusing past perfect with simple past when sequencing past events.