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

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

(A) Steel can be saved

(B) Accidents due to contraction in winter can be avoided

(C) Air gaps are necessary for bearing the weight of running train

(D) Accidents due to expansion in summer can be avoided

Source: This question is taken from the Everyday Science