Correct sentence:
Subway trains run very fast in tunnels.
Why this is better (easy steps):
- Who or what: "Subway trains" — this is the subject (what the sentence is about).
- What they do: "run" — this is the verb (the action).
- Where: "in tunnels" — this tells the place.
- How: "very fast" — this tells the speed. We use "very" instead of "super" because "super" is more informal. For school writing, "very" or "quickly" is better.
Other simple ways to say it:
- Subway trains go very fast through tunnels.
- Subway trains move quickly in tunnels.
- Subways travel fast underground.
Quick tip: Always end the sentence with a period. "Super" is fine when talking with friends, but use "very" or "quickly" for nicer writing.