The oldest meteorite<span> fragments found on </span>Earth<span> are about 4.54 billion years old; this, coupled primarily with the dating of ancient </span>lead<span> deposits, has put the estimated age of Earth at around that time.</span>[38]<span> The </span>Moon<span> has the same composition as Earth's </span>crust<span> but does not contain an </span>iron<span>-rich </span>core<span> like the Earth's.</span>
Answer: a. Genetically significant dose
Explanation:
Genetically significant dose is the index of radiation that is received by the genetic pool. It determines the progeny of the given population. This can be achieved by weighting the individual dose of the gonads that is received by the x-ray examination or ionization imaging by the individuals being examined also by the contribution of those persons to the expected number of children to be born in future.
It represents an estimate of the genetic significance of gonad radiation doses.
Answer:
Systemic gas exchange is the unloading of oxygen and loading of carbon dioxide