In what way does $DNA$ differ from $RNA$?

Who proposed the following statement?
"It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material."

When a chromosome,which appears like beads on a string,is observed under an electron microscope,what is this structure called?

Which one of the following histones is not present in the core particle of the nucleosome?

Given below are two statements:
Statement $I$: In prokaryotes,the positively charged $DNA$ is held with some negatively charged proteins in a region called nucleoid.
Statement $II$: In eukaryotes,the negatively charged $DNA$ is wrapped around the positively charged histone octamer to form nucleosome.
In the light of the above statements,choose the correct answer from the options given below:

If a double stranded $DNA$ has $20\; \%$ of cytosine,what will be the percentage of adenine in it (in $; \%$)?