In short horned cattle, genes for red $(R)$ and white $( r )$ coat colour occur. Cross between red $(RR)$ and white $(rr)$ produced $(Rr)$ roan. This is an example of

If a human mother has ‘$O$' blood group, the foetus would die if the blood of foetus is

A person meets with an accident and great loss of blood has occurred. There is no time to analyse his blood group. It is safe to transfer blood of group

As per $\mathrm{ABO}$ blood grouping system, the blood group of father is $\mathrm{B}^{+}$, mother is $\mathrm{A}^{+}$and child is $\mathrm{O}^{+}$. Their respective genotype can be

Choose the most appropriate answer from the options given below :

In the $ABO$ system, of blood group which of the following is example of co-dominance ?