Yes, this is true.
100% of all children will have a negative blood type.
They cannot. Two parents with type O negative blood will produce offspring of type O negative.
No.
rare
at least one of them have negative group.
yes
They cannot. Two parents with type O negative blood will produce offspring of type O negative.
yes they can
If a child does not have the same blood type as either the father or the mother there is nothing to worry about. It is fairly common for a child to have a blood type that combines the blood types of the parents, such as an AB negative child whose parents had A negative and B negative blood.
Yes, O negative
If both parents have Type B blood the only blood type the child can have is either B or O not looking at whether one of the parents is negative or not.
most probably not.
No.
rare
at least one of them have negative group.
Yes
Yes! Parents have two genes for pos/neg blood type, and only one of them needs to be positive for the parent to have positive blood type. Most positive-blooded people have one positive gene and one negative gene. If both positive parents pass on their negative gene, they can have a child with a negative blood type.
Only if he's adopted. Parents with a + blood type can have children with a - blood type, but parents with an O bloodtypes can only have O type children together.