At what angle is the primary lateral compressive force said to act in tangential compression?

At what angle is the primary lateral compressive force said to act in

1.	At what angle is the primary lateral compressive force said to act in tangential compression?
A.	60 to the trend of the folds
B.	90 to the trend of the folds
C.	30 to the trend of the folds
D.	45 to the trend of the folds
Answer» C. 30 to the trend of the folds