Railways - Engineering

Q1:

Dimensions of a plate girder, are :

A 851 mm x 851 mm

B 255 mm x 254 mm

C 851 mm x 254 mm

D 551 mm x 254 mm

ANS:C - 851 mm x 254 mm

Is it fixed value? I think dimensions of plate girder are depended upon design values for which it is designed.