"both have no direct relationship but a free efficient expression binds them" what are they? (brain game).

Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA)

DNA and RNA are nucleic acids essential for the life of organisms. They are responsible for storing and transporting cellular information in a process known as protein synthesis.

Although DNA and RNA work hand in hand, they have large differences that help them complement each other and function efficiently. That is why it says: "Both have no direct relationship"

When talking about "a free efficient expression binds them" we refer to Gene Expression. It is the process that allows you to obtain proteins from genes, whose final stage is the protein synthesis, which binds both DNA and RNA.

the following key ideas correctly express the key sentence.

restate key idea: most people can learn to swim in ten short lessons.

restate key idea: the majority of water-accident victims require mouth-to-mouth breathing.

restate key idea: an empty, tightly closed gallon jug will support a tired swimmer.  

restate key idea: first aid is to prevent accidents as well as assist in rescue.

explanation: the key idea needs to have the same topic as the key sentence (drowning and safety).

what you where bleeping things out