Answer: Lungs
Explanation: The pleura encloses each lung by a double layered serous membrane
It results in the a narrowing of the arteries which slow blood flow
The number post-reproductive age group will decline in number in a population pyramid.
<h3>What is a population?</h3>
A population is a group of organisms of the same same specie living in a defined area of a given habitat.
A population pyramid shows the number of organisms of age groups in a population.
The post-productive age group is characterized by individuals that are too old to have children.
Since they are too old to have children, the post-reproductive age group will decline in number.
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