[单选题]
The length of a spaceshisg5+i. hve,*t ldz 5ugp is 10 mi61;fpxgooq f:yr.m,*jh 6msg /pj *n when it is at rest. If the spaceship travels by youpi hr.m6of j spg*;oy xg :n,*1m6q/fj with a speed of 0.70c, what length does it appear to you?
A. $5.5 \; m$
B. $7.1 \; m$
C. $12 \; m$
D. $18 \; m$
