Since the 1960s,the Percentage of U

question 10

Multiple Choice

Since the 1960s,the percentage of U.S.output exported to foreigners

• A) remained about the same.
• B) more than doubled.
• C) increased by more than ten times.
• D) declined by about half.

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Definitions:

Neural Crest Cells

A group of embryonic cells found only in vertebrates; develop along the neural tube and migrate to various parts of the embryo where they give rise to (or influence the development of) nerves, head muscles, cranium, jaws, and other structures.

Embryonic Cells

Cells that originate from the embryo and have the potential to develop into any type of body cell, possessing high degrees of plasticity and the ability to proliferate.

Dipnoi

A group of fish also known as lungfish, characterized by their ability to breathe air using lungs in addition to gills.

Actinistia

A subclass of mostly extinct fish, with the modern coelacanths being the only living representatives, characterized by lobed fins.