The HIV virion (viral particle) is a sphere that is roughly 140 nm in diameter. What particular kind of microscope is required to visualize an HIV virion and what is the basis of this microscope’s ability to provide the resolution required to visualize HIV virions.

Electron microscope

Explanation:

Electron microscope uses a beam of electrons as energy source. Since the beam has an exceptionally short wavelength, it strikes most objects in its path and increases the resolution of the microscope significantly. Thus it has a higher magnification and resolution.

for the points

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.