It's a region of DNA that binds DNA Polymerase to begin replication.
Answer:
Social activism will definitely help to fight social challenges as when the whole society comes forward and stand against such challenges it makes the process of eradicating the problems and challenges of society easier. Social challenges are those challenges which the society face as a whole and these challenges are a problem for the whole society and not just a person.
Answer:
Cell membrane as a semi permeable membrane.
Explanation
A semi permeable membrane is the one that would only allow water,ions and certain molecules to pass through it by diffusion while restricting other large molecules from passing through.
Details in the attachment.