What is a disadvantage of the point count method of population monitoring

A disadvantage of the point count method of population monitoring is that it is only beneficial for monitoring organisms, which are fixed in one place.  

The point count method of the population includes standing in a particular position and counting a population of animals, generally birds. The species of birds or the number of birds within a circle of a particular radius is counted.  

The radius is generally formed as big as possible in order to enhance information gathering. This kind of population monitoring can only be utilized for animals, which attain a fixed position, for example, birds thriving in a specific ecosystem.  

(B.) It only records trends in population at fixed locations in the ecosystem. Correct on PLATO

a- all cells come from pre-existing cells

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.