In a railway track, two rails are joined end to end with a gap tin between them because?

1. A Option A: Steel can be saved
2. B Option B: Accidents due to contraction in winter can be avoided
3. C Option C: Air gaps are necessary for bearing the weight of running train
4. D Option D: Accidents due to expansion in summer can be avoided
5. E Option E: All of these

How we write and check questions