The total gap on both sides between the inside edges of wheel flanges and gauge faces of the rail is kept as A. 10 mm B. 13 mm C. 16 mm D. 19 mm

The correct answer is C. 16 mm.

The total gap on both sides between the inside edges of wheel flanges and gauge faces of the rail is kept as 16 mm. This is to ensure that the wheels have enough clearance to pass over the rails without derailing.

Option A is incorrect because it is too small. If the gap is too small, the wheels may rub against the rails and cause derailment.

Option B is incorrect because it is too large. If the gap is too large, the wheels may not have enough traction and the train may derail.

Option D is incorrect because it is not a valid option.