So I don't really understand human blood groups

Check all that are correct about the inheritance of the ABO blood group in humans:

1 The gene for blood type shows a complete dominance inheritance pattern.
2 The gene for blood type shows an incomplete dominance inheritance pattern.
3 The gene for blood type shows a codominance inheritance pattern.
4 The gene for blood type has two different alleles.
5 The gene for blood type has multiple (> 2) alleles.
6 The phenotype for the ABO blood type reflects the types of antibodies produced in the blood stream.
7 The phenotype for the ABO blood type reflects the type of carbohydrate groups found on the surface of red blood cells.
8 A person with type O blood will have compatibility with blood from a type A donor. Hint: Antibodies attack antigens or foreign molecules that are not naturally produced by the individual.
9 A person with type AB blood will have compatibility with blood from a type O donor. Hint: Antibodies attack antigens or foreign molecules that are not naturally produced by the individual.

True false is fine but reasons for the answers would be awesome!

I think 3, 5, 6, 7, and 9 are the true ones but 1-3 confuse me because it seems like blood exhibits co-dominance (AB) and complete dominance (AO or BO).

Thanks!

1. False; there are two co-dominant alleles for blood type (A or B)
2. False; this is co-dominance. Incomplete dominance is when the traits blend; in blood, if both dominant genes are present, the person will have both traits and be type AB.
3.True
4.False; it has three. Type A and type B are co-dominant; type O is recessive to both.
5.True; see above.
6.True; the opposite antibodies will be present. Type A people will have type B antibodies; type B people have type A antibodies, type O people have both A and B antibodies, and type AB people have neither antibody.
7.False. The blood phenotype reflects the presence or absence of A or B antigens, which are proteins and not carbohydrates.