Answer:
a. It is reported in scientific journals and websites
Step-by-step explanation:
Generally, a reliable scientific study should receive wide recommendation from respectable scientist in that domain.
From the options above
The fact your work is base on a famous scientist does not guarantee that your study is reliable .Your work needs to be reviewed by various scientist before it becomes reliable.
A part of a marketing campaign does not project in any way a reliable scientific study
The fact your work is sited by at least one researcher is not a guarantee your work might be a reliable scientific study. The researcher might be a novice too.
The fact your work is reported in scientific journals and websites proves your work is reliable because it has been scrutinize by numerous expert before it was published. This journals and websites have experts in that field that must have verified and seen the lapses before they publish the works.