Why Has Little Progress Been Made in Developing Industry-Standard Traces

Multiple Choice

Why has little progress been made in developing industry-standard traces?

A) Traces are typically proprietary and they rarely are distributed to vendors or to the research community.
B) Trace data is not portable between installations because even small differences in user activity can affect the validity of a trace.
C) For many users, such as those who use personal computers, traces do not yield meaningful performance evaluations.
D) all of the above