A0[m^2]
is the Passarino-Veltman one-point integral .
By default is not expressed in terms of .
[m^2] A0
SetOptions[A0, A0ToB0 -> True];
[m^2] A0
SetOptions[A0, A0ToB0 -> False];
According to the rules of dimensional regularization is set to 0.
[0] A0
[SmallVariable[M^2]] A0