Pick up the correct statement from the following: A. The distance between the points of intersection of the extreme tangents to the transition curve is kept greater than 7500 m × sum of grade changes at the point of intersection B. The rate of change of grade is limited to 0.3% per 30 m length of the curve C. According to I.C.A.O. the maximum longitudinal gradient along a runway is limited to 1.5% D. All the above

The correct answer is D. All the above.

The distance between the points of intersection of the extreme tangents to the transition curve is kept greater than 7500 m × sum of grade changes at the point of intersection. This is to ensure that the transition curve is long enough to allow vehicles to safely change speed and direction.

The rate of change of grade is limited to 0.3% per 30 m length of the curve. This is to ensure that the change in grade is gradual and does not cause vehicles to lose control.

According to I.C.A.O. the maximum longitudinal gradient along a runway is limited to 1.5%. This is to ensure that aircraft can safely take off and land on the runway.

All of these requirements are important for the safety of aircraft and vehicles using the runway.