How do you determine if a certain molecule is polar?
There are multiple ways to determine this. By far the easiest would be to simply draw a lewis structure of the molecule. Based off of the symmetry you can determine if the molecule will either be polar or nonpolar.
What is the basic unit of DNA?
Nucleotides. It is common to mix up the basic functional units of Protein and DNA, but with most things that are biology, you are just going to need to memorize terms. I like to remember by using the N in DNA, with the N in Nucleotides.
Does 2/0= 0?
No. Remember that is very common for people to misunderstand fractions. Many people will see that 0/2= 0 and will think that the reciprocal must also equal 0. Remember that anything divided by 0 is undefined.