A mother has a as her blood type and her husband is o. but their daughter's blood type is b. is that possible?

Clearly yes....: ....It's possible for the baby to be b. But the husband isn't the father. This assumes that you have all the blood types right. Before you stir any pots, i would make very, very sure that the mother and her husband are the blood types you think they are. If mom is actually a or ab, or dad is b, then he could be the father. The baby has to get the b type from someone.

Unlikely: The husband may still be the father if the "B" that the daughter has is a weak "B" unexpressed for whatever reason in the parent. Or the husband may have the bombay phenotype and be unable to express his "B". Or there is a lab error. Or this is indeed non-paternity.