Chen writes, "I received a green card through my parents who used the EB-5 category to invest in a business in the United States. At the time of interview for my citizenship, I was shocked that the interviewing officer asked me more questions about my parents than about me. They wanted to know everything about the investments, where the parents are currently, and what happened to the business they invested in. Do you think my citizenship application will be denied? Is my GC also in jeopardy?"
It is indeed true that the adjudicating officer will review your complete immigration history prior to approving your naturalization. Remember that this is the final chance that the USCIS has to make sure that people who do not deserve to be American citizens are screened out (in rare circumstances, the US Government can denaturalize someone if the citizenship was obtained after hiding material information). Not that they get it right all the time. Every immigrant knows a criminal or a thug or a crook or someone who used fraudulent documents or lied about something with a US passport, but we must agree that the USCIS does the best it can under the tight budget that they have.
Obviously, they do not second-guess the decision of the previous officers who approved the permanent resident status but they do want to make sure that the reason for which the residency was approved was a valid one. A simple example is that of marriage to a US citizen. If the couple is not married for the specified period, it is a red flag. Similarly, someone who got approved for national interest waiver GC based on technical qualifications but is now working as a hairdresser will invite scrutiny from the USCIS. That is why in your case, the USCIS must make sure that your parents did everything right because you derived your green card from them. Since EB5 is highly abused by wealthy foreigners who use it to buy American residency, there is enormous fraud at every stage. If everything is clean with your parents' investment and the green cards were valid, you will be approved. If not, not only will your naturalization denied, your green card can also be taken away.