How do alleles that display codominance differ from alleles that display simple dominance?

A. If two alleles are codominant then both alleles will be expressed in heterozygotes.
B. If two alleles are codominant then the heterozygous phenotype will be somewhere between the homozygous phenotypes.
C. If two alleles display simple dominance then only the recessive allele will be expressed.
D. If two alleles display simple dominance then neither allele will be expressed in heterozygotes.
E. If two alleles display simple dominance then only the dominant allele is inheritable.