Which one of the following can be viewed only by an electron microscope and why ? (cell surface membrane , nucleolus , chromosomes , vacuole )

correct answer is option a.

tropopause, stratopause and mesopause have all in common aspect that is point of maximum temperature in its layer of the atmosphere. all layers of atmosphere observe abrupt change in temperature. tropopause is the boundary between troposphere and stratosphere. stratopause is the boundary between stratosphere and mesosphere. mesopause is the boundary between mesosphere and thermosphere. these all boundaries are ranges between altitude of 0 to 80 km.

for 8 am not sure maybe yes?

for 9 if it is asking if the male is more or less it would be less

hope i even just a little : )