If they had followed the safety protocol, the accident would not have occurred.

226/235

If they were following the safety protocol, the accident would never occur again.

The accident, which happened because they ignored the safety protocol, could not have been avoided.

The accident was so serious that following the safety protocol could hardly have prevented it.

Had they followed the safety protocol, the accident would not have occurred.

Giải thích

Phương pháp giải: Tìm câu có nghĩa tương đương, chú ý các từ khóa và cấu trúc ngữ pháp đặc biệt (đảo ngữ, câu điều kiện).

Giải chi tiết:Câu điều kiện loại 3 (việc đã xảy ra trong quá khứ). Cấu trúc đảo ngữ: "Had + S + V3/ed" tương đương "If + S + had + V3/ed".