Answer:
B. Gathering statistics online
Step-by-step explanation:
Secondary research is basically research that is not "done by you or for you".
B. Gathering statistics online is getting information that was not originally intended for whatever your project is.
A. Hiring a marketing firm to do your research is doing it "for you".
C. Observing reactions to free samples is done "by you".
D. Conducting trial-and-error testing is done "by you".