Genes with high expression levels are more likely to use ________. A: Prefer codons B: Rare codons C: Start codon D: Stop codon

Which of the following statements is correct ( ) A: A total of 20 different codons represent the genetic code; B: Different codons may encode the same amino acid; C: The third bit of the codon has variability. D: Each nucleotide triplet encodes an amino acid;