Answer:
C. 20, one for each amino acid
Step-by-step explanation:
Aminoacyl-tRNA synthetase is an enzyme involved in protein synthesis (translation) with the role to attach suitable amino acid on its tRNA (amino acid that correspond to the anticodon on tRNA). As a result of its action, aminoacyl-tRNA is formed. There are the 20 different types of aminoacyl-tRNA synthethases that make 20 different aminoacyl-tRNA one for each amino acid of the genetic code.