Wich part of a light microscope focuses light onto the specimen through the lens

Why are scientists concerned about the depletion of the ozone levels in the stratosphere?

Does any one know what blood tastes like

Which nutritional supplement is correctly paired with the health issue it addresses? which nutritional supplement is correctly paired with the health issue it addresses? vitamin c supplementation prevent depression. calcium supplementation increases iq. vitamin e supplementation prevent birth defects. vitamin b12 can vegans maintain health?