Answer:
Epithelial cells
Explanation:
Epithelial cells are cells that secret mucus to prevent friction between organs. Like between the Heart and Lung.
Answer:
Limits to variation The most obvious limit to natural selection is that suitable variation may not be available. This may be because certain phenotypes cannot be built, being ruled out either by physical law or by the properties of biological materials.
I hope it's helpful!
The first one is a atom
The second one is a compound
The third one is molecules that are not compounds
The last one is a atom
Answer:
female chimpanzees solicit mates when they are ovulating
