Answer:
A. chromosome
Explanation:
Chromosomes are typically what you see in a chart like karyotype that shows all the chromosomes of a particular organism. These are the highly condensed structures of DNA during replication which makes it easy to transfer DNA during replication.
Answer:
endosymbiosis.
Explanation:
By the beginning of the 20th century, researchers thought that plastids and mitochondria could come from bacteria. These would have been ingested by primitive cells and live within them in symbiosis.
If it is a healthy environment then the atmosphere will be happy meaning no dirty streets etc