The phrase 'had been introduced' is PAST PERFECT PASSIVE tense. Past perfect (had + past participle) is used for an action that happened before another past action. Here, the introduction happened BEFORE the addressing. Example: 'When I arrived, the movie had already started.' (The starting happened before my arrival). The passive voice ('been introduced') tells us the subject received the action.

Break down complex topics into smaller, manageable chunks for easier recall.

Zambia

• Joseph Soko – 101 pts

• Distance of A Straight Line
• Mid-point of A Line
• Equation of a Straight Line
• Parallel and Perpendicular Lines
• COMMUNICATION SYSTEMS