請教Pjiang及各位大俠,關於I-751中的Part4 中的A-number

Part 4 Information about the spouse or parent through whom you gained your conditional residence

My hu*****and is an US citizen, he has a A number when he applied his green card several years ago. When I fill in the I-751 form about his information , A-Number (if any) ,which answer I should choose

1.His previous A number

2.None

3.N/A

4.Just leave this answer blank

Thank you in advance for your help.