The Short Lifetime of Muons Created in the Upper Atmosphere

Multiple Choice

The short lifetime of muons created in the upper atmosphere of the Earth would not allow them to reach the surface of the Earth unless their lifetime increased by time dilation.From the reference system of the muons,the muons can reach the surface of the Earth because

A) time dilation increases their velocity.
B) time dilation increases their energy.
C) length contraction decreases the distance to the Earth.
D) the relativistic speed of the Earth toward them is added to their velocity.