The correct answer is D. All of the above.
The validity and reliability of a research will be at stake when the author who is the source of information is biased, incompetent or dishonest, the incident was reported after a long period of time from that of its occurrence, and the researcher himself is not competent enough to draw logical conclusions.
A biased author may not report the information accurately or objectively. An incompetent or dishonest author may make up information or distort the truth. If the incident was reported after a long period of time, it is possible that the information is inaccurate or incomplete. And if the researcher himself is not competent enough to draw logical conclusions, the results of the research may be flawed.
It is important to be aware of these potential problems when evaluating research. If you are unsure about the validity or reliability of a research study, you should consult with a qualified expert.