The important things to remember are that chromosomes as well as genes occur in ...$A$.... The two alleles of a gene pair are located on homologous sites on ...$B$... chromosomes. Choose the correct choice for $A$ and $B$.

• A
  $A$-single,$B$-analogous
• B
  $A$-pair,$B$-analogous
• C
  $A$-pair,$B$-homologous
• D
  $A$-single,$B$-heterozygous