Pick up the correct statement from the following:

• The distance between the points of intersection of the extreme tangents to the transition curve is kept greater than 7500 m x sum of grade changes at the point of intersection
• The rate of change of grade is limited to 0.3% per 30 m length of the curve
• According to I.C.A.O. the maximum longitudinal gradient along a runway is limited to 1.5%
• All the above.