The red bluebird controls its feather color with a single allele they can be blue (dominant) or red (recessive). What are the genotypes of the offspring.

A all BB

B all Bb

C all bb

D one BB two B one bb

The genotype of the offspring depends on the genotype of the parents which is missing from the question.

If the two parents have the genotypes BB and BB, the offspring will all have the genotype BB.

If the two parents have the genotypes Bb and Bb, the offspring will be 1 BB, 2 Bb and 1 bb.

If the two parents have the genotypes bb and bb, all the offspring will be of genotype bb.

If the two parents have the genotypes BB and bb, all the offspring will have the genotype Bb.

If the two parents have the genotype Bb and bb, the offspring will have the genotypes 1 Bb and 1 bb.

If the two parents have the genotype BB and Bb, the off spring will have the genotypes 1 BB and 1 Bb.

You can see that there are many situations depends on the genotype of the offspring. Therefore, the genotype of the offspring must be defined in the question.