What is the metallic layer at the earth's center

Which of the following best describes the purpose of a nation’s boundaries? a. to limit the movement of goods and people b. to make it easier for cartographers to create maps c. to make the movement of goods and people easier d. to prevent other countries from invading territory

What is the climate of the himalayas? a. cold and wet c. cold and dry b. hot and humid d. hot and dry

Who developed the theory of plate tectonics?