When Using the Time Order of Occurrence of Variables as Evidence

When using the time order of occurrence of variables as evidence of a causal relationship between two variables

A) it is possible for each term in the relationship to be both a "cause" and an effect of the other term.
B) the occurrence of a causal factor must follow the occurrence of the event.
C) it is fairly easy for the researcher to understand the time sequence governing a phenomenon.
D) an effect can be produced by an event that occurs after the effect has taken place.
E) a relationship between the two variables can be proved.