From where did the oxygen in the Earth's atmosphere originate?
A) photosynthesis from plant life and single-celled organisms
B) atmospheric bombardment
C) outgassing from volcanoes
D) chemical reactions between gas in the upper atmosphere and the solar wind
E) oxidation of surface rocks
A
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The kilowatt-hour is a unit of ______________
Fill in the blank(s) with correct word
Weight and g: In another solar system, a planet has an airless moon Zygo that is 4.0 × 105 m in diameter. Experiments reveal that a freely falling object at the surface of Zygo accelerates at 0.20 m/s2. What is the mass of Zygo? (G = 6.67 × 10-11 N ? m2/kg2)
A. 2.4 × 1019 kg B. 4.8 × 1019 kg C. 1.2 × 1020 kg D. 2.4 × 1020 kg E. 4.8 × 1020 kg
Find the orbital speed of an ice cube in the rings of Saturn. The mass of Saturn is 5.68 x 1026 kg, and use an orbital radius of 1.00 x 105 km. (G = 6.67 × 10-11 N ? m2/kg2)
A) 19.5 km/s B) 27.5 km/s C) 13.8 km/s
Radioactivity Basics: Starting with 
U, assume that the following three decays occur in sequence:(1) alpha decay(2) beta-minus decay(3) alpha decayDetermine the correct isotope that is left after each decay.
What will be an ideal response?