Final answer:
During the translation of a 100-amino acid polypeptide, 99 amino acids enter through the A site of the ribosome, with the first amino acid entering at the P site.
Step-by-step explanation:
The question concerns the number of amino acids that enter through the A site of the ribosome during the translation of a polypeptide that is 100 amino acids in length. During translation elongation, the ribosome shifts one codon at a time. Each time an amino acid is added to the growing polypeptide chain, a charged tRNA brings the new amino acid into the ribosome through the A site. The first amino acid enters at the P site, and the following 99 enter at the A site before moving to the P site to be added to the polypeptide chain.
The correct answer to how many amino acids entered through the A site of the ribosome during the translation is d) 99.