Questions: Parents do not have marriage certificate for I-130

At old time, marriage certificate is optional, so my parents did not get one.

Now they are both here, and I want to file I-130 for them. I want to use the way mentioned in the form about "What If a Document Is Not Available?" (see below)

Here are my questions:
1. Where should I go for "a statement from the appropriate civil authority certifying that the document or documents are not available.", should the statement be notarized in China?

2. Is option C a valid secondary evidence? If yes, is "HuKouBen" for this purpose?

3. In option D, should the statements be notarized in China?

Thanks a lot!


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In the form, it says If a Document Is Not Available:

In such situation, a statement from the appropriate civil authority certifying that the document or documents are not available. You must also secondary evidence,including:

C. Census record: State or Federal census record showing the names, place of birth, date of birth or the age of the person listed.

D. Affidavits: Written statements sworn to or affirmed bytwo persons who were living at the time and who havepersonal knowledge of the event you are trying to prove.For example, the date and place of birth, marriage ordeath. The person making the affidavit does not have tobe a U.S. citizen. Each affidavit should contain thefollowing information regarding the person making theaffidavit: his or her full name, address, date and place ofbirth and his or her relationship to you, if any, fullinformation concerning the event, and complete detailsexplaining how the person acquired knowledge of theevent.