What are the correct fill ins?

Blank is a naturally occurring gas that's found in most soils and rocks and can cause lung cancer

Find the equation of the line passing through the point (–1, 5) and perpendicular to the line 3x + y = 4.

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