✨ ベストアンサー ✨
すべての英文を倒置の形にすればいいので
1. Never have I heard anything bad about Shinkansen trains.
2. Rarely have we seen dust in his room.
3. Few foreign passangers do we see in the local train.
4. Only to clean his room did he buy an expensive robot cleaner.
だとおもいます