100 mm
122.2 mm
136.5 mm
146.0 mm
Answer is Wrong!
Answer is Right!
The correct answer is B. 122.2 mm.
The width of foot for 90 R rail section is 122.2 mm. This is the distance between the two inner edges of the rail’s foot. The foot is the part of the rail that rests on the rail bed. The width of the foot is important because it determines the amount of support that the rail receives from the rail bed. A wider foot provides more support, which can help to prevent the rail from derailing.
The other options are incorrect because they do not represent the actual width of foot for 90 R rail section. Option A is 100 mm, which is too narrow. Option C is 136.5 mm, which is too wide. Option D is 146.0 mm, which is also too wide.