In a traditionally drawn decision tree,a circle represents ().
A.a chance to which no estimated monetary value can be assigned so that a likely pay-off can not be shown
B.a decision to which no estimated monetary value can be assigned so that a likely pay-off can not be shown
C.a chance to which an estimated monetary value may be assigned to calculate the most likely pay-off
D.a decision to which an estimated monetary value may be assigned to calculate the most likely pay-off