Which scientist's observations were the basis for the rule that the ratio between Adenine and Thymine,and Guanine and Cytosine in $DNA$ remains constant and equal to one another?

When was $DNA$ first discovered?

Who proposed the double helix model of $DNA$?

If the base sequence in one strand of $DNA$ is "$ATCGA$", what is the total number of $H$-bonds present in the $DNA$ double helix?

Read the following statements and choose the set of correct statements:
$(a)$ Euchromatin stains light.
$(b)$ Heterochromatin is transcriptionally inactive.
$(c)$ Histone octamer contains eight molecules of histone proteins.
$(d)$ Packaging of chromatin at higher level requires additional set of proteins that are referred to as non-histone chromosomal $(NHC)$ proteins.
$(e)$ In a human diploid cell,$6.6 \times 10^9$ base pairs are present,not $6.6 \times 10$ nucleosomes.
Choose the correct answer from the options given below:

The unit of inheritance is.