<span> the atmosphere holds about 21 per cent oxygen. Over the Earth’s 4.6 billion year history, oxygen did not appear in the atmosphere until perhaps about 2.5 billion years ago. Since then, oxygen levels have fluctuated in tandem with global geological and biological events, such as mass extinctions.</span>
Answer:
C. The child must have inherited sickle cell genes from both parents.
Explanation:
Because of the fact that sickle cell disease is recessive, the child would have to get the gene from both parents.
IVA: nonmetal/other metals VIIA:halogens VIII: Nobel Gases
