Correct Answer - D
`**` From the very beginning of the proposition of code, it was clear to Francis Crick that there has to be a mechanism to read the code and also to link it to the amino acids, because amino acids have no structural specialties to read the code uniquely.
`**` He postulated the presence of an adapter molecule that would on one hand read the code and on other hand would bind to specific amino acids.
`**` The tRNA, then called sRNA (soluble RNA), was known before the genetic code was postulated.
