If the stress ratio is given by R, and the amplitude ratio is given by A, the ratio between the R and A is given as __________

If the stress ratio is given by R, and the amplitude ratio is given by

1.	If the stress ratio is given by R, and the amplitude ratio is given by A, the ratio between the R and A is given as __________
A.	A=R
B.	A=1/R
C.	A=(1-R)/(1+R)
D.	A=(1+R)/(1-R)
Answer» D. A=(1+R)/(1-R)