Which of the following was not developed until the early part of the twentieth century

How do you transfer mrna into codons ? i'm so confused : (

How do chloroplasts set plants apart from other living things

What are the possible blood types among the children of parents that are ab and ii? oa) types a and b ob) types a, b, and ab c) types a, b, and o od) types a, b, ab, and o