The Short Lifetime of Muons Created in the Upper Atmosphere

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