 
			 
			MCQOPTIONS
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				| 1. | The earth is able to retain its atmosphere because of _____ | 
| A. | the mean velocities of atmospheric gas molecules which is less than that of the earth s escape velocity | 
| B. | the mean velocities of atmospheric gas molecules which is greater than that of the earth s escape velocity | 
| C. | the gravitational effect of the moon | 
| D. | the earth s magnetic field | 
| Answer» B. the mean velocities of atmospheric gas molecules which is greater than that of the earth s escape velocity | |