About numbers

The following data about number of girls in a family was recorded. A family is chosen at random. Find the probability of having 2 girls in the chosen family.

Which statements (s) about oxidation number is (are) correct?

Which of the following statement about quantum number is correct ?

Which of the following statement about quantum number is wrong ?

About the total number of species present on earth, a more conservative and scientifically sound estimate made by

A more conservative and scientifically sound estimate about the total number of species present on earth, was made by