Which of the following is not a reason for depletion of free hydrogen in Earth`s lower atmosphere

题目

Which of the following is not a reason for depletion of free hydrogen in Earth`s lower atmosphere
A.Hydrogen being the lightestelement buoys to the upper most layer of earth`s atmosphere and leaks out.
B.All hydrogen atoms will havespeeds greater than the escape velocity of earth and so they escape earth`sgravitational pull.
C.Even those hydrogen atoms withspeeds less than the Escape velocity eventually acquire enough Kinetic Energyto escape the Earth`s pull,due to energy exchange during collisions events.
D.Some hydrogen atoms have speedsgreater than Earth`s escape velocity and so they escape Earth`s gravitationalpull

答案

选 B
不是所有的氢原子都具有如此大的速度