Sickle-cell disease is common in tropical and sub-tropical regions because being a carrier, carrying a single sickle-cell mutation (sickle cell trait), affords some resistance to malaria.
Covalent bond is when two atoms share one or more pairs of electrons, an example of this could be H20 or C02.
ionic bonds are when one or more electrons from am atom are removed and attached to another, which can result in positive or negative ions which attract each other, an example of this could be table salt.
D. Mitochondria and Chloroplast
i'm sorry if it's wrong but that should be the right answer
They mainly target airway epithelial cells
When fossil fuels are burned they can cause pollution which can cause global warming.
