Who proposed the semi-conservative replication of $DNA$?

The experimental proof for semiconservative replication of $DNA$ was first shown in a:

Depending upon the chemical nature of the template ($DNA$ or $RNA$) and the nature of nucleic acids synthesized from it ($DNA$ or $RNA$),list the types of nucleic acid polymerases.

Replication was allowed to take place in the presence of radioactive deoxynucleotide precursors in $E. coli$ that was a mutant for $DNA$ ligase. Newly synthesised radioactive $DNA$ was purified and strands were separated by denaturation. These were centrifuged using density gradient centrifugation. Which of the following would be a correct result?

On which of the following did Taylor and his colleagues perform their experiments?

$DNA$ multiplication is called: