In a bb x bb cross

a.
100% of the offspring will have the bb genotype
c.
75% of the offspring will have the bb phenotype
b.
25% of the offspring will have the bb genotype
d.
50% of the offspring will have the bb phenotype

a.

100% of the offspring will have the Bb genotype

Explanation:

This cross involves a single gene that has two alternative forms called ALLELES. One allele is 'B' and the other is 'b'. In the cross, both parents are purebreeding or homozygous i.e. they contain identical alleles for a particular trait (BB and bb). Therefore, according to Mendel's law of segregation, the alleles of each parent will separate into gametes during meiosis.

Parent 'BB' will produce gametes containing allele 'B' while parent 'bb' will produce gametes containing allele 'b'. Each gametes will then combine randomly. Since only gametes B and b are produced by each parent, all the offsprings produced will have a heterozygous genotype: Bb. Hence, 100% of the F1 offsprings will possess Bb genotype.

c.muti cella's eukaryotic organisms began to diversify

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.