11. The major constituents of the Earth's current atmosphere are a. moslty oxygen with some CO2
b. 78% oxygen, 21% nitrogen
C.78% nitrogen, 21% oxygen

12. The Earth's primitive atmosphere
a. was primarily hydrogen and helium, like the giant planets'
b. escaped due to the Earth's rapid loss of heat from its interior
C. was mostly carbon dioxide, since plants hadn't yet formed to add oxygen

13. The Earth's magnetic field stretches out in an area called the
A. Magnetosphere
b. Troposphere
C. Atmosphere